Porretta was born in Darien, Connecticut, into a show-biz family: his father, Frank Porretta, was a famous opera singer and musical theater actor. His mother, Roberta, is also a trained singer and was Miss Ohio 1956.

Porretta wasted no time in getting involved with the entertainment industry. By the age of 25 he was already a veteran of Broadway and a student at the Manhattan School of Music. In 1990 Porretta broke into television with recurring roles on shows like Wings and Beverly Hills, 90210. In 1993 he was given his first major movie role, as Will Scarlet O'Hara in Mel Brooks' spoof Robin Hood: Men in Tights. Interestingly, Porretta would star as Robin Hood in his own TV series four years later. Since 1997 he has starred in many independent movies and been featured in commercials for McDonald's and Arrowhead Water. In 1994 he appeared in the original Broadway cast of Stephen Sondheim and James Lapine's Passion.

In August 2009 it was revealed that he would be the voice actor of the protagonist in the video game title Alan Wake, a psychological action thriller developed by Remedy Entertainment.

He has been in a relationship with Gleice with whom he was married from 2012 to 2014. Matthew and Gleice have two sons, Luigi (2001) and Enzo (2009). The couple divorced and split up in 2014.