Nassib called the decision, after seven seasons in the league, "bittersweet," saying he was retiring from football to focus on his company Rayze.
"Football has given me more than I ever could have imagined," he wrote in an Instagram post. "I can truly hang up my helmet for the last time knowing I gave it everything I had.
"Growing up I loved how fun football was. I loved the pursuit of perfection. I loved the small window where every player has to chase their dreams. It makes it all the more exciting if you get there. It was always my dream to play in the NFL, even as a walk-on, and I really feel like the luckiest guy on the planet."
Nassib, a third-round draft selection by Cleveland in 2016, spent two years with the Browns then played two seasons with the Tampa Bay Buccaneers.
He signed with the Raiders in 2020 and played two seasons with them before rejoining Tampa Bay for 13 games last season.
He came out as gay in 2021, becoming the first active NFL player to do so.
Michael Sam had been the first openly gay player selected in the NFL Draft, taken by the then-St. Louis Rams in 2014.
Sam played pre-season games for the Rams and was briefly on the practice squad of the Dallas Cowboys, but never suited up for a regular-season contest.
"Big moments like this are a time for gratitude," Nassib wrote. "I want to thank God, my family and my friends for always being there for me even when I didn't realize it.
"I want to thank my agent Brian Ayrault. Staying with you to WME was one of the best decisions I have ever made. Brian was the first person in the football industry I came out to and he didn't blink. He encouraged and motivated me to follow through with my announcement and to make as big of an impact as I possibly could."
Amid thanks to coaches and team executives, teammates, trainers and other team staff he worked with over the years, Nassib offered advice to "anyone who has a dream of being the best, never let anyone convince you it's impossible. Be the best you can be in everything you do. Work hard, make smart decisions and be kind to others."
