Sam Asghari traded the gym for the runway Tuesday night ... strutting his stuff at the Blue Jacket Fashion Show ... it's all on video, and it was all for a good cause.

Sam walked in the 10th anniversary celebration at W Hollywood Tuesday night, joining a stylish lineup of celebrities, designers and advocates who came together to raise awareness for prostate cancer and men's health.

Video and photos from the event show Sam confidently walking the runway ... going shirtless under a blazer.

The annual event uses fashion to spark conversations about early detection and supports ZERO Prostate Cancer, a nonprofit focused on research, education and health equity.

Sam appeared to be right at home under the runway lights ... proving he can serve looks just as easily as he serves action hero muscles.

Seriously, the dude is jacked.

The Blue Jacket Fashion Show was founded by designer Frederick Anderson ... and Sam wasn't the only famous face walking the runway.

Other stars that walked included Gleb Savchenko, Ian Ziering, Brett Brown, and Everett Osborne ... just to name a few.