With the Excel file open select File in the top-left corner of the screen, followed by Info. Select Protect Workbook, then choose Encrypt with Password.

How do I password-protect an Excel file on desktop? To password-protect an Excel file or Excel Workbook on your Windows 11/10 desktop, follow these steps: ...

While password protection and encryption are excellent ways to secure your Excel workbook, they aren't foolproof and may cause compatibility issues with some third-party applications.