Sylvester Stallone Celebrates Daughter Sistine's High School Graduation -- See the Sweet Pic!

Sylvester Stallone is one proud papa!
The Creed star attended his 18-year-old daughter Sistine's high school graduation on Saturday, commemorating the milestone moment on Instagram, writing, "Our Sistine graduates! Congratulations to a wonderful young lady!"

Sistine's mom, Jennifer Flavin Stallone, also celebrated, writing, "Sistine's graduation!🎉 You are hard-working, smart, and kind💜-always being a good person is what I am most proud of!⭐️#goodness #compassionate #caring."

Turn that tassle from left to right, Sistine -- congrats!
Meanwhile, ET caught up with Sistine, as well as Sly's other two daughters, Sophie, 20, and Scarlet, 14, at their Harper's Bazaar cover party in April, where they were put to the test about how well they know their famous father.
Watch the video below for more.