diff --git a/.changeset/deep-knives-tie.md b/.changeset/deep-knives-tie.md
new file mode 100644
index 000000000..5adf33e8f
--- /dev/null
+++ b/.changeset/deep-knives-tie.md
@@ -0,0 +1,19 @@
+---
+"@slack/web-api": minor
+---
+
+feat: add `highlight_type` to [`files.completeUploadExternal`](https://docs.slack.dev/reference/methods/files.completeUploadExternal) and [`filesUploadV2`](https://docs.slack.dev/tools/node-slack-sdk/web-api#upload-a-file) for optimistic rendering
+
+```js
+import { WebClient } from "@slack/web-api";
+
+const client = new WebClient(process.env.SLACK_BOT_TOKEN);
+
+await client.filesUploadV2({
+  channel_id: "C0123456789",
+  file: "./image.png",
+  filename: "image.png",
+  title: "Image Upload",
+  highlight_type: "png",
+});
+```
diff --git a/packages/web-api/src/file-upload.test.ts b/packages/web-api/src/file-upload.test.ts
index bc14885d5..e9902e333 100644
--- a/packages/web-api/src/file-upload.test.ts
+++ b/packages/web-api/src/file-upload.test.ts
@@ -316,6 +316,28 @@ describe('file-upload', () => {
     });
   });
   describe('getAllFileUploadsToComplete', () => {
+    it('should pass all expected properties through to the completion job', () => {
+      const fileUploadJob1 = {
+        file: Buffer.from('test'),
+        filename: 'image.png',
+        file_id: 'id1',
+        title: 'test1',
+        channel_id: 'C123',
+        thread_ts: '1.0',
+        initial_comment: 'Here is an image',
+        highlight_type: 'png',
+        blocks: [{ type: 'section', text: { type: 'plain_text', text: 'hello' } }],
+      };
+      const toComplete = getAllFileUploadsToComplete([fileUploadJob1]);
+      const job = Object.values(toComplete)[0];
+      assert.strictEqual(job.files[0].id, 'id1');
+      assert.strictEqual(job.files[0].title, 'test1');
+      assert.strictEqual(job.channel_id, 'C123');
+      assert.strictEqual(job.thread_ts, '1.0');
+      assert.strictEqual(job.initial_comment, 'Here is an image');
+      assert.strictEqual(job.files[0].highlight_type, 'png');
+      assert.deepStrictEqual(job.blocks, fileUploadJob1.blocks);
+    });
     describe('when channel_id is the same', () => {
       it('should group uploads with matching thread_ts and initial_comment together', () => {
         const fileUploadJob1 = {
diff --git a/packages/web-api/src/file-upload.ts b/packages/web-api/src/file-upload.ts
index b8b44e424..b6beade2d 100644
--- a/packages/web-api/src/file-upload.ts
+++ b/packages/web-api/src/file-upload.ts
@@ -30,6 +30,7 @@ export async function getFileUploadJob(
     blocks: options.blocks,
     channel_id: options.channels ?? options.channel_id,
     filename: options.filename ?? fileName,
+    highlight_type: options.highlight_type,
     initial_comment: options.initial_comment,
     snippet_type: options.snippet_type,
     title: options.title ?? options.filename ?? fileName, // default title to filename unless otherwise specified
@@ -234,13 +235,13 @@ export function getAllFileUploadsToComplete(
 ): Record<string, FilesCompleteUploadExternalArguments> {
   const toComplete: Record<string, FilesCompleteUploadExternalArguments> = {};
   for (const upload of fileUploads) {
-    const { blocks, channel_id, thread_ts, initial_comment, file_id, title } = upload;
+    const { blocks, channel_id, thread_ts, highlight_type, initial_comment, file_id, title } = upload;
     if (file_id) {
       const compareString = `:::${channel_id}:::${thread_ts}:::${initial_comment}:::${JSON.stringify(blocks)}`;
       // biome-ignore lint/suspicious/noPrototypeBuiltins: TODO use hasOwn instead of hasOwnProperty
       if (!Object.prototype.hasOwnProperty.call(toComplete, compareString)) {
         toComplete[compareString] = {
-          files: [{ id: file_id, title }],
+          files: [{ id: file_id, title, highlight_type }],
           channel_id,
           blocks,
           initial_comment,
@@ -262,6 +263,7 @@ export function getAllFileUploadsToComplete(
         toComplete[compareString].files.push({
           id: file_id,
           title,
+          highlight_type,
         });
       }
     } else {
diff --git a/packages/web-api/src/types/request/files.ts b/packages/web-api/src/types/request/files.ts
index e891bff6d..3d05ddd7f 100644
--- a/packages/web-api/src/types/request/files.ts
+++ b/packages/web-api/src/types/request/files.ts
@@ -34,6 +34,11 @@ export interface FileType {
 export interface FileUploadComplete {
   /** @description Encoded file ID. */
   id: string;
+  /**
+   * @description Optional highlight type hint for the file. The upload processing job may overwrite this value.
+   * @see {@link https://docs.slack.dev/reference/methods/files.completeUploadExternal}
+   */
+  highlight_type?: string;
   /** @description File title. */
   title?: string;
 }
@@ -168,6 +173,11 @@ export type FileUploadV2 = FileUpload & {
   channel_id?: string;
   /** @deprecated use channel_id instead */
   channels?: string;
+  /**
+   * @description Optional highlight type hint for the file. The upload processing job may overwrite this value.
+   * @see {@link https://docs.slack.dev/reference/methods/files.completeUploadExternal}
+   */
+  highlight_type?: string;
   /** @description Syntax type of the snippet being uploaded. E.g. `python`. */
   snippet_type?: string;
 };