"Happy Birthday to my TV little sister and real life soul sister, @beverleymitchell! Hope today is filled with all the good good you can handle. Love you! 🎂🎈🎉," she captioned the sweet picture of the girls.
Both stars found fame on the family show which ran between 1996 and 2007.
Biel, 35, and Mitchell, 37, played sisters Mary and Lucy Camden.
While we know Biel is currently winning fans over in Netflix hit The Sinner, Mitchell is also working on a comedic show called Hollywood Darlings.
This article previously appeared on WHO.