The comedy series' renewal was announced at the Television Critics Association's winter TV previews, reported Ace Showbiz.
The network ordered a 12-episode season of 'Shameless'. The fifth season premiere aired on January 11.
"The viewer loyalty and critical acclaim over the last five seasons has made 'Shameless' one of our signature series," Showtime's president David Nevins announced.
"This incredible collection of writers and actors have created a show truly unique in the television landscape."
The network also confirmed the series pick-up of Happyish starring Steve Coogan. The 10-episode season will debut on April 26.