Marini was born in Grasse, Alpes-Maritimes, France, to a Greek mother and Italian father. He worked as a baker in his father’s bakery from the age of eight. After completing high school, he joined the French army and was stationed in Paris, where he served as a fireman in the Paris Fire Brigade. There, Marini met Fred Goudon, a photographer who introduced him to the world of modeling. After fulfilling his military duties in his early twenties, he went to the United States to learn English while working as a model. One of his first jobs was a television commercial for Bud Light beer. He made his acting debut at the age of 29, in the 2005 horror film Screech of the Decapitated.

Marini played Dante in Sex and the City: The Movie, and has appeared on Brothers & Sisters, Ugly Betty, Dirty Sexy Money, Criminal Minds, Nip/Tuck, The Bold and the Beautiful, Passions, and 2 Broke Girls. His film credits include One and the Other (L’Une et L’Autre) and The Boys & Girls Guide to Getting Down. On February 8, 2009, it was announced that Marini would participate in the eighth season of Dancing with the Stars. His professional partner was Cheryl Burke. He also took part in the fifteenth season of Dancing with the Stars for another chance to win the mirrorball trophy. He danced with season fourteen winner, Peta Murgatroyd. They were the eighth couple eliminated from the competition, alongside Kirstie Alley and Maksim Chmerkovskiy.

In 2009, Marini was introduced as a recurring character on ABC’s family drama Brothers & Sisters. He played Luc Laurent, the French love interest of Rachel Griffiths’ character Sarah Walker, in what was slated to be a five-episode arc, but was promoted to series regular in 2010. Brothers & Sisters was cancelled by ABC in May 2011, after the fifth season ended. He also appeared as Bay Kennish’s biological father, Angelo Sorrento, in Switched at Birth. On September 18, 2012, it was announced that he would become a series regular for the second season.

Marini and his professional partner, Cheryl Burke, came in as the runners-up of the eighth season of the American televised ballroom dancing competition Dancing with the Stars. On May 19, 2009, then seventeen-year-old gymnast Shawn Johnson and her partner, Mark Ballas, were crowned champions of that season, defeating Marini & Burke by 1%.