The Pepperdine University business major clearly inherited his dad's athleticism, showing off his chiseled chest and canon arm in the California sun.
This comes after photos of Baena and his father working out in the gym together surfaced on the internet last month.
Schwarzenegger fathered his son with his former housekeeper, Mildred Baena. The action star has four additional children with estranged wife, Maria Shriver -- 26-year-old Katherine, 24-year-old Christina, 22-year-old Patrick, and 18-year-old Christopher.
Arnold was all smiles as Patrick graduated from the Marshall School of Business at the University of Southern California over the weekend.
"Patrick, I'm so proud of you," Arnold wrote in the caption of an Instagram pic. "You have grown into a great man -- physically and mentally -- and I can't wait to see what you do next. Congratulations. I love you."