diff --git a/internal/endtoend/testdata/on_duplicate_key_update/mysql/db/db.go b/internal/endtoend/testdata/on_duplicate_key_update/mysql/db/db.go
new file mode 100644
index 0000000000..c3c034ae37
--- /dev/null
+++ b/internal/endtoend/testdata/on_duplicate_key_update/mysql/db/db.go
@@ -0,0 +1,29 @@
+// Code generated by sqlc. DO NOT EDIT.
+
+package db
+
+import (
+	"context"
+	"database/sql"
+)
+
+type DBTX interface {
+	ExecContext(context.Context, string, ...interface{}) (sql.Result, error)
+	PrepareContext(context.Context, string) (*sql.Stmt, error)
+	QueryContext(context.Context, string, ...interface{}) (*sql.Rows, error)
+	QueryRowContext(context.Context, string, ...interface{}) *sql.Row
+}
+
+func New(db DBTX) *Queries {
+	return &Queries{db: db}
+}
+
+type Queries struct {
+	db DBTX
+}
+
+func (q *Queries) WithTx(tx *sql.Tx) *Queries {
+	return &Queries{
+		db: tx,
+	}
+}
diff --git a/internal/endtoend/testdata/on_duplicate_key_update/mysql/db/models.go b/internal/endtoend/testdata/on_duplicate_key_update/mysql/db/models.go
new file mode 100644
index 0000000000..3bc48237ef
--- /dev/null
+++ b/internal/endtoend/testdata/on_duplicate_key_update/mysql/db/models.go
@@ -0,0 +1,13 @@
+// Code generated by sqlc. DO NOT EDIT.
+
+package db
+
+import (
+	"database/sql"
+)
+
+type Author struct {
+	ID   int64
+	Name string
+	Bio  sql.NullString
+}
diff --git a/internal/endtoend/testdata/on_duplicate_key_update/mysql/db/query.sql.go b/internal/endtoend/testdata/on_duplicate_key_update/mysql/db/query.sql.go
new file mode 100644
index 0000000000..4f2406ac33
--- /dev/null
+++ b/internal/endtoend/testdata/on_duplicate_key_update/mysql/db/query.sql.go
@@ -0,0 +1,27 @@
+// Code generated by sqlc. DO NOT EDIT.
+// source: query.sql
+
+package db
+
+import (
+	"context"
+	"database/sql"
+)
+
+const upsertAuthor = `-- name: UpsertAuthor :exec
+INSERT INTO authors (name, bio)
+VALUES (?, ?)
+ON DUPLICATE KEY
+    UPDATE bio = ?
+`
+
+type UpsertAuthorParams struct {
+	Name  string
+	Bio   sql.NullString
+	Bio_2 sql.NullString
+}
+
+func (q *Queries) UpsertAuthor(ctx context.Context, arg UpsertAuthorParams) error {
+	_, err := q.db.ExecContext(ctx, upsertAuthor, arg.Name, arg.Bio, arg.Bio_2)
+	return err
+}
diff --git a/internal/endtoend/testdata/on_duplicate_key_update/mysql/query.sql b/internal/endtoend/testdata/on_duplicate_key_update/mysql/query.sql
new file mode 100644
index 0000000000..25b98d3b15
--- /dev/null
+++ b/internal/endtoend/testdata/on_duplicate_key_update/mysql/query.sql
@@ -0,0 +1,13 @@
+-- https://github.com/kyleconroy/sqlc/issues/921
+CREATE TABLE authors (
+  id   BIGINT  NOT NULL AUTO_INCREMENT PRIMARY KEY,
+  name text    NOT NULL,
+  bio  text,
+  UNIQUE(name)
+);
+
+-- name: UpsertAuthor :exec
+INSERT INTO authors (name, bio)
+VALUES (?, ?)
+ON DUPLICATE KEY
+    UPDATE bio = ?;
diff --git a/internal/endtoend/testdata/on_duplicate_key_update/mysql/sqlc.json b/internal/endtoend/testdata/on_duplicate_key_update/mysql/sqlc.json
new file mode 100644
index 0000000000..0895d9fa2e
--- /dev/null
+++ b/internal/endtoend/testdata/on_duplicate_key_update/mysql/sqlc.json
@@ -0,0 +1,11 @@
+{
+	"version":"1",
+	"packages":[
+		{
+			"path":"db",
+			"engine":"mysql",
+			"schema":"query.sql",
+			"queries":"query.sql"
+		}
+	]
+}
diff --git a/internal/endtoend/testdata/on_duplicate_key_update/postgresql/db/db.go b/internal/endtoend/testdata/on_duplicate_key_update/postgresql/db/db.go
new file mode 100644
index 0000000000..c3c034ae37
--- /dev/null
+++ b/internal/endtoend/testdata/on_duplicate_key_update/postgresql/db/db.go
@@ -0,0 +1,29 @@
+// Code generated by sqlc. DO NOT EDIT.
+
+package db
+
+import (
+	"context"
+	"database/sql"
+)
+
+type DBTX interface {
+	ExecContext(context.Context, string, ...interface{}) (sql.Result, error)
+	PrepareContext(context.Context, string) (*sql.Stmt, error)
+	QueryContext(context.Context, string, ...interface{}) (*sql.Rows, error)
+	QueryRowContext(context.Context, string, ...interface{}) *sql.Row
+}
+
+func New(db DBTX) *Queries {
+	return &Queries{db: db}
+}
+
+type Queries struct {
+	db DBTX
+}
+
+func (q *Queries) WithTx(tx *sql.Tx) *Queries {
+	return &Queries{
+		db: tx,
+	}
+}
diff --git a/internal/endtoend/testdata/on_duplicate_key_update/postgresql/db/models.go b/internal/endtoend/testdata/on_duplicate_key_update/postgresql/db/models.go
new file mode 100644
index 0000000000..3bc48237ef
--- /dev/null
+++ b/internal/endtoend/testdata/on_duplicate_key_update/postgresql/db/models.go
@@ -0,0 +1,13 @@
+// Code generated by sqlc. DO NOT EDIT.
+
+package db
+
+import (
+	"database/sql"
+)
+
+type Author struct {
+	ID   int64
+	Name string
+	Bio  sql.NullString
+}
diff --git a/internal/endtoend/testdata/on_duplicate_key_update/postgresql/db/query.sql.go b/internal/endtoend/testdata/on_duplicate_key_update/postgresql/db/query.sql.go
new file mode 100644
index 0000000000..d96cde7f11
--- /dev/null
+++ b/internal/endtoend/testdata/on_duplicate_key_update/postgresql/db/query.sql.go
@@ -0,0 +1,26 @@
+// Code generated by sqlc. DO NOT EDIT.
+// source: query.sql
+
+package db
+
+import (
+	"context"
+	"database/sql"
+)
+
+const upsertAuthor = `-- name: UpsertAuthor :exec
+INSERT INTO authors (name, bio)
+VALUES ($1, $2)
+ON CONFLICT (name) DO UPDATE
+SET bio = $2
+`
+
+type UpsertAuthorParams struct {
+	Name string
+	Bio  sql.NullString
+}
+
+func (q *Queries) UpsertAuthor(ctx context.Context, arg UpsertAuthorParams) error {
+	_, err := q.db.ExecContext(ctx, upsertAuthor, arg.Name, arg.Bio)
+	return err
+}
diff --git a/internal/endtoend/testdata/on_duplicate_key_update/postgresql/query.sql b/internal/endtoend/testdata/on_duplicate_key_update/postgresql/query.sql
new file mode 100644
index 0000000000..b2a51c5f42
--- /dev/null
+++ b/internal/endtoend/testdata/on_duplicate_key_update/postgresql/query.sql
@@ -0,0 +1,12 @@
+-- https://github.com/kyleconroy/sqlc/issues/921
+CREATE TABLE authors (
+  id   BIGSERIAL PRIMARY KEY,
+  name text      NOT NULL UNIQUE,
+  bio  text
+);
+
+-- name: UpsertAuthor :exec
+INSERT INTO authors (name, bio)
+VALUES ($1, $2)
+ON CONFLICT (name) DO UPDATE
+SET bio = $2;
diff --git a/internal/endtoend/testdata/on_duplicate_key_update/postgresql/sqlc.json b/internal/endtoend/testdata/on_duplicate_key_update/postgresql/sqlc.json
new file mode 100644
index 0000000000..00a8a0fcfd
--- /dev/null
+++ b/internal/endtoend/testdata/on_duplicate_key_update/postgresql/sqlc.json
@@ -0,0 +1,11 @@
+{
+	"version":"1",
+	"packages":[
+		{
+			"path":"db",
+			"engine":"postgresql",
+			"schema":"query.sql",
+			"queries":"query.sql"
+		}
+	]
+}
diff --git a/internal/engine/dolphin/convert.go b/internal/engine/dolphin/convert.go
index 6f8236e1c7..4cf484c60a 100644
--- a/internal/engine/dolphin/convert.go
+++ b/internal/engine/dolphin/convert.go
@@ -407,6 +407,18 @@ func (c *cc) convertInsertStmt(n *pcast.InsertStmt) *ast.InsertStmt {
 			ValuesLists: c.convertLists(n.Lists),
 		}
 	}
+
+	if n.OnDuplicate != nil {
+		targetList := &ast.List{}
+		for _, a := range n.OnDuplicate {
+			targetList.Items = append(targetList.Items, c.convertAssignment(a))
+		}
+		insert.OnConflictClause = &ast.OnConflictClause{
+			TargetList: targetList,
+			Location:   n.OriginTextPosition(),
+		}
+	}
+
 	return insert
 }