The pair have not been offered new contracts to play on next season and will be forced to find a new club.
Ferrante was part of the Melbourne Victory squad that won the 2006/07 A-League title but moved onto Wellington the following season and has been there ever since but after failing to grab a regular spot in midfield this season, has been told he is no longer required.
27-year old Mulligan came to Wellington from English club Port Vale in July 2008 after almost a decade in the English Football League with Barnsley, Doncaster Rovers, Scunthorpe United and Grimsby Town.
Despite being born in England, he has represented the New Zealand national team on 25 occasions but unfortunately won't be at the Phoenix next term.
Wellington chief executive Tony Pignata thanked the pair for their efforts and was confident their careers would continue.
"The club thanks Michael and David for everything they've done," Pignata said. "Michael, in particular, has been an important member of the squad and was a foundation player for the Phoenix. I'm sure that both Michael and David will be able to continue their careers at other clubs."