If you don't ever plan on using Calibri again the following hack will force OneNote to use the font of your choice. 1 Close OneNote if its runningn2 Go to and remove all the Calibri fonts. There are about 5-6. Take a TTF file of the font you want (Helvetica for example) and rename it to and paste it in this directoryn4 To be safe open Font Book app (use Spotlight to find it) and delete Calibri as well Re-open OneNote and it should be using your new font even in your existing notes. Unfortunately the default size of the font is still not adjustable. If OneNote updates itself from the App Store you will most likely need to repeat the above as it will reinstall Calibri. But a small relief from this ugly MS font!