diff --git a/src/cursor/abstract_cursor.ts b/src/cursor/abstract_cursor.ts
index 95b8bdaef7c..de3a0cb9775 100644
--- a/src/cursor/abstract_cursor.ts
+++ b/src/cursor/abstract_cursor.ts
@@ -841,7 +841,10 @@ function cleanupCursor(
 
     if (session) {
       if (session.owner === cursor) {
-        return session.endSession({ error }, callback);
+        session.endSession({ error }).finally(() => {
+          callback();
+        });
+        return;
       }
 
       if (!session.inTransaction()) {
@@ -855,10 +858,11 @@ function cleanupCursor(
   function completeCleanup() {
     if (session) {
       if (session.owner === cursor) {
-        return session.endSession({ error }, () => {
+        session.endSession({ error }).finally(() => {
           cursor.emit(AbstractCursor.CLOSE);
           callback();
         });
+        return;
       }
 
       if (!session.inTransaction()) {
@@ -872,11 +876,13 @@ function cleanupCursor(
 
   cursor[kKilled] = true;
 
-  return executeOperation(
+  executeOperation(
     cursor[kClient],
-    new KillCursorsOperation(cursorId, cursorNs, server, { session }),
-    completeCleanup
-  );
+    new KillCursorsOperation(cursorId, cursorNs, server, { session })
+  ).finally(() => {
+    completeCleanup();
+  });
+  return;
 }
 
 /** @internal */
diff --git a/src/encrypter.ts b/src/encrypter.ts
index 8fe18aa3675..ee95f0ba1bf 100644
--- a/src/encrypter.ts
+++ b/src/encrypter.ts
@@ -1,4 +1,5 @@
 /* eslint-disable @typescript-eslint/no-var-requires */
+
 import { deserialize, serialize } from './bson';
 import { MONGO_CLIENT_EVENTS } from './constants';
 import type { AutoEncrypter, AutoEncryptionOptions } from './deps';
@@ -114,7 +115,11 @@ export class Encrypter {
     this.autoEncrypter.teardown(!!force, e => {
       const internalClient = this[kInternalClient];
       if (internalClient != null && client !== internalClient) {
-        return internalClient.close(force, callback);
+        internalClient.close(force).then(
+          () => callback(),
+          error => callback(error)
+        );
+        return;
       }
       callback(e);
     });
diff --git a/src/operations/bulk_write.ts b/src/operations/bulk_write.ts
index 627dc709a70..f56fd8c5a17 100644
--- a/src/operations/bulk_write.ts
+++ b/src/operations/bulk_write.ts
@@ -52,15 +52,10 @@ export class BulkWriteOperation extends AbstractOperation<BulkWriteResult> {
     }
 
     // Execute the bulk
-    bulk.execute({ ...options, session }, (err, r) => {
-      // We have connection level error
-      if (!r && err) {
-        return callback(err);
-      }
-
-      // Return the results
-      callback(undefined, r);
-    });
+    bulk.execute({ ...options, session }).then(
+      result => callback(undefined, result),
+      error => callback(error)
+    );
   }
 }
 
diff --git a/src/operations/collections.ts b/src/operations/collections.ts
index 8b314865a92..14a1ccbb3c7 100644
--- a/src/operations/collections.ts
+++ b/src/operations/collections.ts
@@ -25,24 +25,26 @@ export class CollectionsOperation extends AbstractOperation<Collection[]> {
     session: ClientSession | undefined,
     callback: Callback<Collection[]>
   ): void {
-    const db = this.db;
-
     // Let's get the collection names
-    db.listCollections(
-      {},
-      { ...this.options, nameOnly: true, readPreference: this.readPreference, session }
-    ).toArray((err, documents) => {
-      if (err || !documents) return callback(err);
-      // Filter collections removing any illegal ones
-      documents = documents.filter(doc => doc.name.indexOf('$') === -1);
-
-      // Return the collection objects
-      callback(
-        undefined,
-        documents.map(d => {
-          return new Collection(db, d.name, db.s.options);
-        })
+    this.db
+      .listCollections(
+        {},
+        { ...this.options, nameOnly: true, readPreference: this.readPreference, session }
+      )
+      .toArray()
+      .then(
+        documents => {
+          const collections = [];
+          for (const { name } of documents) {
+            if (!name.includes('$')) {
+              // Filter collections removing any illegal ones
+              collections.push(new Collection(this.db, name, this.db.s.options));
+            }
+          }
+          // Return the collection objects
+          callback(undefined, collections);
+        },
+        error => callback(error)
       );
-    });
   }
 }
diff --git a/src/operations/common_functions.ts b/src/operations/common_functions.ts
index a439aca7eb4..63f7e1f2525 100644
--- a/src/operations/common_functions.ts
+++ b/src/operations/common_functions.ts
@@ -69,12 +69,15 @@ export function indexInformation(
   // Get the list of indexes of the specified collection
   db.collection(name)
     .listIndexes(options)
-    .toArray((err, indexes) => {
-      if (err) return callback(err);
-      if (!Array.isArray(indexes)) return callback(undefined, []);
-      if (full) return callback(undefined, indexes);
-      callback(undefined, processResults(indexes));
-    });
+    .toArray()
+    .then(
+      indexes => {
+        if (!Array.isArray(indexes)) return callback(undefined, []);
+        if (full) return callback(undefined, indexes);
+        callback(undefined, processResults(indexes));
+      },
+      error => callback(error)
+    );
 }
 
 export function prepareDocs(
diff --git a/src/operations/indexes.ts b/src/operations/indexes.ts
index 3a3b72dc30c..8d095e16501 100644
--- a/src/operations/indexes.ts
+++ b/src/operations/indexes.ts
@@ -1,7 +1,7 @@
 import type { Document } from '../bson';
 import type { Collection } from '../collection';
 import type { Db } from '../db';
-import { MongoCompatibilityError, MONGODB_ERROR_CODES, MongoServerError } from '../error';
+import { MongoCompatibilityError, MONGODB_ERROR_CODES, MongoError } from '../error';
 import type { OneOrMore } from '../mongo_types';
 import { ReadPreference } from '../read_preference';
 import type { Server } from '../sdam/server';
@@ -320,22 +320,23 @@ export class EnsureIndexOperation extends CreateIndexOperation {
   override execute(server: Server, session: ClientSession | undefined, callback: Callback): void {
     const indexName = this.indexes[0].name;
     const cursor = this.db.collection(this.collectionName).listIndexes({ session });
-    cursor.toArray((err, indexes) => {
-      /// ignore "NamespaceNotFound" errors
-      if (err && (err as MongoServerError).code !== MONGODB_ERROR_CODES.NamespaceNotFound) {
-        return callback(err);
-      }
-
-      if (indexes) {
+    cursor.toArray().then(
+      indexes => {
         indexes = Array.isArray(indexes) ? indexes : [indexes];
         if (indexes.some(index => index.name === indexName)) {
           callback(undefined, indexName);
           return;
         }
+        super.execute(server, session, callback);
+      },
+      error => {
+        if (error instanceof MongoError && error.code === MONGODB_ERROR_CODES.NamespaceNotFound) {
+          // ignore "NamespaceNotFound" errors
+          return super.execute(server, session, callback);
+        }
+        return callback(error);
       }
-
-      super.execute(server, session, callback);
-    });
+    );
   }
 }
 
diff --git a/src/operations/is_capped.ts b/src/operations/is_capped.ts
index 938c72f41cf..1219e79cf72 100644
--- a/src/operations/is_capped.ts
+++ b/src/operations/is_capped.ts
@@ -28,15 +28,17 @@ export class IsCappedOperation extends AbstractOperation<boolean> {
         { name: coll.collectionName },
         { ...this.options, nameOnly: false, readPreference: this.readPreference, session }
       )
-      .toArray((err, collections) => {
-        if (err || !collections) return callback(err);
-        if (collections.length === 0) {
-          // TODO(NODE-3485)
-          return callback(new MongoAPIError(`collection ${coll.namespace} not found`));
-        }
+      .toArray()
+      .then(
+        collections => {
+          if (collections.length === 0) {
+            // TODO(NODE-3485)
+            return callback(new MongoAPIError(`collection ${coll.namespace} not found`));
+          }
 
-        const collOptions = collections[0].options;
-        callback(undefined, !!(collOptions && collOptions.capped));
-      });
+          callback(undefined, !!collections[0].options?.capped);
+        },
+        error => callback(error)
+      );
   }
 }
diff --git a/src/operations/options_operation.ts b/src/operations/options_operation.ts
index 27853d34edb..9c053938bf3 100644
--- a/src/operations/options_operation.ts
+++ b/src/operations/options_operation.ts
@@ -29,14 +29,17 @@ export class OptionsOperation extends AbstractOperation<Document> {
         { name: coll.collectionName },
         { ...this.options, nameOnly: false, readPreference: this.readPreference, session }
       )
-      .toArray((err, collections) => {
-        if (err || !collections) return callback(err);
-        if (collections.length === 0) {
-          // TODO(NODE-3485)
-          return callback(new MongoAPIError(`collection ${coll.namespace} not found`));
-        }
+      .toArray()
+      .then(
+        collections => {
+          if (collections.length === 0) {
+            // TODO(NODE-3485)
+            return callback(new MongoAPIError(`collection ${coll.namespace} not found`));
+          }
 
-        callback(err, collections[0].options);
-      });
+          callback(undefined, collections[0].options);
+        },
+        error => callback(error)
+      );
   }
 }