In 2002, when she was 16 years old, Ozawa debuted in a 30-second Japanese TV commercial for DARS Chocolate alongside two members of the Japanese pop group KinKi Kids. Ozawa is featured sharing chocolate with one of the two singers while secretly holding hands with the other.
In August 2008, Ozawa acted in her first mainstream movie, Invitation Only, billed as "Taiwan's First-Ever Slasher Horror". The film is produced by Three Dots Entertainment in Taipei, Taiwan and co-stars Julianne Chu. Ozawa plays a supermodel. She spoke both English and Japanese. Ozawa's professionalism impressed her co-workers and her role was expanded to include further scenes. Maria Ozawa also did a photoshoot for the Taiwanese version of FHM in May 2009.
Ozawa followed up on her Shinjuku experience by starring in a cabaret show, "Tokyo Nights" at the Grand Lisboa Hotel in Macao from August 16 to September 6, 2008 which also featured several other Japanese performers. "Tokyo Nights" received mixed reviews. Promotional materials show her with a temporary tattoo.
Ozawa began to be cast in a variety of videos from different producers, including her first exclusively lesbian (Rezu - レズ) video (W Cast Premium Lesbian) for LADYxLADY, a division of the Japanese porn conglomerate Soft On Demand (SOD).
In November 2011, Ozawa co-starred with Asami and AV actress Mahiro Aine in Naoyuki Tomomatsu's science fiction V-Cinema release Karei naru erogami-ke no ichizoku: Shinsō reijō wa denki shitsuji no yume o miru ka, which was also released with English subtitles as Erotibot. She was also cast in the starring role for the erotic horror V-cinema feature Tokyo Species which was released on DVD in February 2012.