Mosley’s announcement comes one month after he lost a unanimous decision to junior middleweight champ Saul “Canelo” Alvarez of Mexico.
“Good morning everybody. Just want to thank you for showing me so much love,” Mosley wrote on his social networking Twitter site. “Had a great career and loved every moment of it, win, lose or draw.”
The 40-year-old Mosley’s career included a memorable welterweight championship win in 2000 over Oscar De La Hoya.
He now plans to became a trainer to his 21-year-old son.
“I’m going into the promotional world, I’m training my son. It was a helluva career. I’m happy for all the great memories and all the great fighters that I fought. Now it’s time give back. I’m ready to train my son full-time now,” Mosley told ESPN.com.
Mosley, of the US, is one of the few boxers of his era to have never been knocked out.
He finished with a 46-8-1 record, but was 0-3-1 over his last four fights.