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How to Update Project Online Custom Fields using Power Automate

Maira Mehtab Sep 21, 2026 869 views

Question details

The user needs to automate the updating of a custom field across more than 100 Project Online projects using Power Apps and Power Automate.

Product: Project Online, Power Automate
Device & OS: not provided
Scenario: Building a bulk-update automation flow where listing, checking out, and retrieving projects work, but the final update operation fails.
Observed behavior: The Power Automate flow successfully executes preliminary project management steps (checkout, data retrieval) but encounters a failure during the custom field update action.

Before you start

Ensure that the account running the Power Automate flow has the necessary administrative permissions in Project Online to check out and edit enterprise projects.

Solution 1Recommended

Use the Project Online REST API Endpoint

Call the specific UpdateCustomFields endpoint via a SharePoint HTTP request to reliably update project attributes.

Standard Power Automate connectors sometimes struggle with deep Project Online custom field updates. Bypassing these by using the Project Server REST API directly via a SharePoint HTTP request provides the exact control needed to push updates.

Set up a Power Apps V2 Trigger

In Power Automate, create a new flow and select the 'Power Apps (V2)' trigger so you can initiate the bulk update directly from a button click inside your Power App.

Check out the Project

Use an HTTP request to call the project checkout endpoint before attempting any modifications. The project must be in a checked-out draft state to accept changes.

Call the UpdateCustomFields Endpoint

Add a 'Send an HTTP request to SharePoint' action. Set the method to POST and use the URI: `/_api/ProjectServer/Projects('<guid>')/Draft/UpdateCustomFields()`. Replace `<guid>` with your dynamic project ID variable.

Check in and Publish

Once the update request succeeds, use subsequent HTTP requests to check the project back in and publish it so the custom field changes reflect globally across your Project Online environment.

Payload Formatting: Make sure your JSON body in the HTTP request is formatted exactly as the REST API expects, referencing the internal field names of the custom fields rather than their display names.

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Frequently Asked Questions

Why does my UpdateCustomFields API call return an error?

This usually happens if the project is not successfully checked out beforehand, or if the JSON payload references the incorrect internal field name for the custom field.

Can I use standard Project Online connectors instead of HTTP requests?

While standard connectors exist for basic actions like creating projects or tasks, they often lack the depth required to update specific enterprise custom fields, making the REST API via HTTP requests the most reliable method.

Do I need a premium Power Automate license to use the SharePoint HTTP request?

No, the 'Send an HTTP request to SharePoint' action is typically a standard connector, allowing you to interact with the Project Online API without requiring premium licensing.

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