The rep for the actress and PEOPLE StyleWatch Celeb Council Member has confirmed the engagement of the couple, who have been dating for about six months, reports E! News.
Rivera, 26, showed off her new sparkler from Big Sean, 25, at Latina magazine's Hollywood Hot List Party Oct. 3. Rivera dons the cover of the October issue.
The couple have admitted they met on Twitter, sending messages back and forth, until 140 characters just wouldn't cut it anymore.
"I had followed him, and he sent me a little message like, 'I'm a fan,' " Rivera told Access Hollywood last month. "We went to dinner and the rest is history."