The 31-year-old scored against Manchester United on his City debut but failed to make an impact at Eastlands after that and spent the second half of last season on loan at Sunderland.
Benjani scored seven goals in 31 appearances for City following his 3.8 million pounds move from Portsmouth in January 2008.
Mancini, planning for an influx of new signings during the close-season, has also released Bulgaria midfielder Martin Petrov and Brazilian left-back Sylvinho.
“Martin Petrov, Sylvinho and Benjani are senior players who will leave City this summer. All three are out of contract and free to negotiate deals at new clubs,” a statement on City’s website confirmed.
Petrov endured an injury-hit spell with City following his move to Eastlands from Atletico Madrid in 2007 and was a bit-part player this season, not playing for them after suffering a knee injury in February.
He was on 45,000 pounds a week at City but has attracted interest from Premier League outfits Bolton Wanderers and West Ham.
Sylvinho helped Barcelona win the Champions League in 2006 and 2009, but the 35-year-old made just nine starts for Mancini’s men after his move from Spain. AFP