diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..260e34a
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,476 @@
+// Type definitions for Node OAuth2 Server 4.0
+// Definitions by:  Robbie Van Gorkom <https://github.com/vangorra>,
+//                  Charles Irick <https://github.com/cirick>,
+//                  Daniel Fischer <https://github.com/d-fischer>,
+//                  Vitor Santos <https://github.com/rvitorsantos>
+
+import * as http from 'http';
+
+/**
+ * Represents an OAuth2 server instance.
+ */
+declare class OAuth2Server {
+    static OAuth2Server: typeof OAuth2Server;
+
+    /**
+     * Instantiates OAuth2Server using the supplied model
+     */
+    constructor(options: OAuth2Server.ServerOptions);
+
+    /**
+     * Authenticates a request.
+     */
+    authenticate(
+        request: OAuth2Server.Request,
+        response: OAuth2Server.Response,
+        options?: OAuth2Server.AuthenticateOptions,
+        callback?: OAuth2Server.Callback<OAuth2Server.Token>
+    ): Promise<OAuth2Server.Token>;
+
+    /**
+     * Authorizes a token request.
+     */
+    authorize(
+        request: OAuth2Server.Request,
+        response: OAuth2Server.Response,
+        options?: OAuth2Server.AuthorizeOptions,
+        callback?: OAuth2Server.Callback<OAuth2Server.AuthorizationCode>
+    ): Promise<OAuth2Server.AuthorizationCode>;
+
+    /**
+     * Retrieves a new token for an authorized token request.
+     */
+    token(
+        request: OAuth2Server.Request,
+        response: OAuth2Server.Response,
+        options?: OAuth2Server.TokenOptions,
+        callback?: OAuth2Server.Callback<OAuth2Server.Token>
+    ): Promise<OAuth2Server.Token>;
+}
+
+declare namespace OAuth2Server {
+    /**
+     * Represents an incoming HTTP request.
+     */
+    class Request {
+        body?: any;
+        headers?: { [key: string]: string; } | undefined;
+        method?: string | undefined;
+        query?: { [key: string]: string; } | undefined;
+
+        /**
+         * Instantiates Request using the supplied options.
+         *
+         */
+        constructor(options?: { [key: string]: any } | http.IncomingMessage);
+
+        /**
+         * Returns the specified HTTP header field. The match is case-insensitive.
+         *
+         */
+        get(field: string): any | undefined;
+
+        /**
+         * Checks if the request’s Content-Type HTTP header matches any of the given MIME types.
+         *
+         */
+        is(types: string[]): string | false;
+    }
+
+    /**
+     * Represents an outgoing HTTP response.
+     */
+    class Response {
+        body?: any;
+        headers?: { [key: string]: string; } | undefined;
+        status?: number | undefined;
+
+        /**
+         * Instantiates Response using the supplied options.
+         *
+         */
+        constructor(options?: { [key: string]: any; } | http.ServerResponse);
+
+        /**
+         * Returns the specified HTTP header field. The match is case-insensitive.
+         *
+         */
+        get(field: string): any | undefined;
+
+        /**
+         * Sets the specified HTTP header field. The match is case-insensitive.
+         *
+         */
+        set(field: string, value: string): void;
+
+        /**
+         * Redirects to the specified URL using 302 Found.
+         *
+         */
+        redirect(url: string): void;
+    }
+
+    abstract class AbstractGrantType {
+        /**
+         * Instantiates AbstractGrantType using the supplied options.
+         *
+         */
+        constructor(options: TokenOptions)
+
+        /**
+         * Generate access token. Calls Model#generateAccessToken() if implemented.
+         *
+         */
+        generateAccessToken(client: Client, user: User, scope: string | string[]): Promise<string>;
+
+        /**
+         * Generate refresh token. Calls Model#generateRefreshToken() if implemented.
+         *
+         */
+        generateRefreshToken(client: Client, user: User, scope: string | string[]): Promise<string>;
+
+        /**
+         * Get access token expiration date.
+         *
+         */
+        getAccessTokenExpiresAt(): Date;
+
+        /**
+         * Get refresh token expiration date.
+         *
+         */
+        getRefreshTokenExpiresAt(): Date;
+
+        /**
+         * Get scope from the request body.
+         *
+         */
+        getScope(request: Request): string;
+
+        /**
+         * Validate requested scope. Calls Model#validateScope() if implemented.
+         *
+         */
+        validateScope(user: User, client: Client, scope: string | string[]): Promise<string | string[] | Falsey>;
+
+        /**
+         * Retrieve info from the request and client and return token
+         *
+         */
+        abstract handle(request: Request, client: Client): Promise<Token | Falsey>;
+    }
+
+    interface ServerOptions extends AuthenticateOptions, AuthorizeOptions, TokenOptions {
+        /**
+         * Model object
+         */
+        model: AuthorizationCodeModel | ClientCredentialsModel | RefreshTokenModel | PasswordModel | ExtensionModel;
+    }
+
+    interface AuthenticateOptions {
+        /**
+         * The scope(s) to authenticate.
+         */
+        scope?: string | string[] | undefined;
+
+        /**
+         * Set the X-Accepted-OAuth-Scopes HTTP header on response objects.
+         */
+        addAcceptedScopesHeader?: boolean | undefined;
+
+        /**
+         * Set the X-OAuth-Scopes HTTP header on response objects.
+         */
+        addAuthorizedScopesHeader?: boolean | undefined;
+
+        /**
+         * Allow clients to pass bearer tokens in the query string of a request.
+         */
+        allowBearerTokensInQueryString?: boolean | undefined;
+    }
+
+    interface AuthorizeOptions {
+        /**
+         * The authenticate handler
+         */
+        authenticateHandler?: {} | undefined;
+
+        /**
+         * Allow clients to specify an empty state
+         */
+        allowEmptyState?: boolean | undefined;
+
+        /**
+         * Lifetime of generated authorization codes in seconds (default = 5 minutes).
+         */
+        authorizationCodeLifetime?: number | undefined;
+    }
+
+    interface TokenOptions {
+        /**
+         * Lifetime of generated access tokens in seconds (default = 1 hour)
+         */
+        accessTokenLifetime?: number | undefined;
+
+        /**
+         * Lifetime of generated refresh tokens in seconds (default = 2 weeks)
+         */
+        refreshTokenLifetime?: number | undefined;
+
+        /**
+         * Allow extended attributes to be set on the returned token
+         */
+        allowExtendedTokenAttributes?: boolean | undefined;
+
+        /**
+         * Require a client secret. Defaults to true for all grant types.
+         */
+        requireClientAuthentication?: {} | undefined;
+
+        /**
+         * Always revoke the used refresh token and issue a new one for the refresh_token grant.
+         */
+        alwaysIssueNewRefreshToken?: boolean | undefined;
+
+        /**
+         * Additional supported grant types.
+         */
+        extendedGrantTypes?: { [key: string]: typeof AbstractGrantType } | undefined;
+    }
+
+    /**
+     * Represents a generic callback structure for model callbacks
+     */
+    type Callback<T> = (err?: any, result?: T) => void;
+
+    /**
+     * For returning falsey parameters in cases of failure
+     */
+    type Falsey = '' | 0 | false | null | undefined;
+
+    interface BaseModel {
+        /**
+         * Invoked to generate a new access token.
+         *
+         */
+        generateAccessToken?(client: Client, user: User, scope: string | string[], callback?: Callback<string>): Promise<string>;
+
+        /**
+         * Invoked to retrieve a client using a client id or a client id/client secret combination, depending on the grant type.
+         *
+         */
+        getClient(clientId: string, clientSecret: string, callback?: Callback<Client | Falsey>): Promise<Client | Falsey>;
+
+        /**
+         * Invoked to save an access token and optionally a refresh token, depending on the grant type.
+         *
+         */
+        saveToken(token: Token, client: Client, user: User, callback?: Callback<Token>): Promise<Token | Falsey>;
+    }
+
+    interface RequestAuthenticationModel {
+        /**
+         * Invoked to retrieve an existing access token previously saved through Model#saveToken().
+         *
+         */
+        getAccessToken(accessToken: string, callback?: Callback<Token>): Promise<Token | Falsey>;
+
+        /**
+         * Invoked during request authentication to check if the provided access token was authorized the requested scopes.
+         *
+         */
+        verifyScope(token: Token, scope: string | string[], callback?: Callback<boolean>): Promise<boolean>;
+    }
+
+    interface AuthorizationCodeModel extends BaseModel, RequestAuthenticationModel {
+        /**
+         * Invoked to generate a new refresh token.
+         *
+         */
+        generateRefreshToken?(client: Client, user: User, scope: string | string[], callback?: Callback<string>): Promise<string>;
+
+        /**
+         * Invoked to generate a new authorization code.
+         *
+         */
+        generateAuthorizationCode?(client: Client, user: User, scope: string | string[], callback?: Callback<string>): Promise<string>;
+
+        /**
+         * Invoked to retrieve an existing authorization code previously saved through Model#saveAuthorizationCode().
+         *
+         */
+        getAuthorizationCode(authorizationCode: string, callback?: Callback<AuthorizationCode>): Promise<AuthorizationCode | Falsey>;
+
+        /**
+         * Invoked to save an authorization code.
+         *
+         */
+        saveAuthorizationCode(
+          code: Pick<AuthorizationCode, 'authorizationCode' | 'expiresAt' | 'redirectUri' | 'scope'>,
+          client: Client,
+          user: User,
+          callback?: Callback<AuthorizationCode>): Promise<AuthorizationCode | Falsey>;
+
+        /**
+         * Invoked to revoke an authorization code.
+         *
+         */
+        revokeAuthorizationCode(code: AuthorizationCode, callback?: Callback<boolean>): Promise<boolean>;
+
+        /**
+         * Invoked to check if the requested scope is valid for a particular client/user combination.
+         *
+         */
+        validateScope?(user: User, client: Client, scope: string | string[], callback?: Callback<string | Falsey>): Promise<string | string[] | Falsey>;
+    }
+
+    interface PasswordModel extends BaseModel, RequestAuthenticationModel {
+        /**
+         * Invoked to generate a new refresh token.
+         *
+         */
+        generateRefreshToken?(client: Client, user: User, scope: string | string[], callback?: Callback<string>): Promise<string>;
+
+        /**
+         * Invoked to retrieve a user using a username/password combination.
+         *
+         */
+        getUser(username: string, password: string, callback?: Callback<User | Falsey>): Promise<User | Falsey>;
+
+        /**
+         * Invoked to check if the requested scope is valid for a particular client/user combination.
+         *
+         */
+        validateScope?(user: User, client: Client, scope: string | string[], callback?: Callback<string | Falsey>): Promise<string | string[] | Falsey>;
+    }
+
+    interface RefreshTokenModel extends BaseModel, RequestAuthenticationModel {
+        /**
+         * Invoked to generate a new refresh token.
+         *
+         */
+        generateRefreshToken?(client: Client, user: User, scope: string | string[], callback?: Callback<string>): Promise<string>;
+
+        /**
+         * Invoked to retrieve an existing refresh token previously saved through Model#saveToken().
+         *
+         */
+        getRefreshToken(refreshToken: string, callback?: Callback<RefreshToken>): Promise<RefreshToken | Falsey>;
+
+        /**
+         * Invoked to revoke a refresh token.
+         *
+         */
+        revokeToken(token: RefreshToken | Token, callback?: Callback<boolean>): Promise<boolean>;
+    }
+
+    interface ClientCredentialsModel extends BaseModel, RequestAuthenticationModel {
+        /**
+         * Invoked to retrieve the user associated with the specified client.
+         *
+         */
+        getUserFromClient(client: Client, callback?: Callback<User | Falsey>): Promise<User | Falsey>;
+
+        /**
+         * Invoked to check if the requested scope is valid for a particular client/user combination.
+         *
+         */
+        validateScope?(user: User, client: Client, scope: string | string[], callback?: Callback<string | Falsey>): Promise<string | string[] | Falsey>;
+    }
+
+    interface ExtensionModel extends BaseModel, RequestAuthenticationModel {}
+
+    /**
+     * An interface representing the user.
+     * A user object is completely transparent to oauth2-server and is simply used as input to model functions.
+     */
+    interface User {
+        [key: string]: any;
+    }
+
+    /**
+     * An interface representing the client and associated data
+     */
+    interface Client {
+        id: string;
+        redirectUris?: string | string[] | undefined;
+        grants: string | string[];
+        accessTokenLifetime?: number | undefined;
+        refreshTokenLifetime?: number | undefined;
+        [key: string]: any;
+    }
+
+    /**
+     * An interface representing the authorization code and associated data.
+     */
+    interface AuthorizationCode {
+        authorizationCode: string;
+        expiresAt: Date;
+        redirectUri: string;
+        scope?: string | string[] | undefined;
+        client: Client;
+        user: User;
+        [key: string]: any;
+    }
+
+    /**
+     * An interface representing the token(s) and associated data.
+     */
+    interface Token {
+        accessToken: string;
+        accessTokenExpiresAt?: Date | undefined;
+        refreshToken?: string | undefined;
+        refreshTokenExpiresAt?: Date | undefined;
+        scope?: string | string[] | undefined;
+        client: Client;
+        user: User;
+        [key: string]: any;
+    }
+
+    /**
+     * An interface representing the refresh token and associated data.
+     */
+    interface RefreshToken {
+        refreshToken: string;
+        refreshTokenExpiresAt?: Date | undefined;
+        scope?: string | string[] | undefined;
+        client: Client;
+        user: User;
+        [key: string]: any;
+    }
+
+    class OAuthError extends Error {
+        constructor(messageOrError: string | Error, properties?: object);
+
+        /**
+         * The HTTP error code.
+         */
+        code: number;
+
+        /**
+         * The OAuth error code.
+         */
+        name: string;
+
+        /**
+         * A human-readable error message.
+         */
+        message: string;
+    }
+
+    class AccessDeniedError extends OAuthError {}
+    class InsufficientScopeError extends OAuthError {}
+    class InvalidArgumentError extends OAuthError {}
+    class InvalidClientError extends OAuthError {}
+    class InvalidGrantError extends OAuthError {}
+    class InvalidRequestError extends OAuthError {}
+    class InvalidScopeError extends OAuthError {}
+    class InvalidTokenError extends OAuthError {}
+    class ServerError extends OAuthError {}
+    class UnauthorizedClientError extends OAuthError {}
+    class UnauthorizedRequestError extends OAuthError {}
+    class UnsupportedGrantTypeError extends OAuthError {}
+    class UnsupportedResponseTypeError extends OAuthError {}
+}
+
+export = OAuth2Server;
diff --git a/package.json b/package.json
index beaeb89..7cede2a 100644
--- a/package.json
+++ b/package.json
@@ -17,6 +17,7 @@
     "Daniel Reguero"
   ],
   "main": "index.js",
+  "types": "index.d.ts",
   "dependencies": {
     "basic-auth": "2.0.1",
     "bluebird": "3.7.2",