The couple, who have been dating for less than six months, posted matching photos on Instagram of Mena wearing a diamond ring on her finger, reported Ace Showbiz.
Mena has also thanked fans on Twitter for their congratulatory messages.
The couple are said to have met on the music video show 106 & Park, which Bow Wow hosts.
Bow Wow - real name Shad Moss - is working on a new album and was recently cast in 'CSI: Cyber'.
Mena is known for being a cast member on American reality series 'Love & Hip-Hop', which is expected to return in November.