Pisi was born in Samoa but moved to Auckland in New Zealand aged 3 with his family.[2] He went to West Harbour Primary School and Massey High School where captained their rugby team,[3] and represented New Zealand Schools.
Pisi made his provincial debut playing for North Harbour in 2005 alongside his elder brother Tusi Pisi. He made 50 appearances for North Harbour before transferring to Taranaki for the 2010 ITM Cup. He made 18 appearances for the Blues between 2006 and 2010, but didn't record a try and never fully established himself as a starter.
He moved to France in February 2011 as a medical joker for Gavin Williams,[4] and then moved on to sign for Northampton for the 2011/12 season, and was named in the Aviva Premiership Dream Team during his first season at the club.[5] In 2014 Pisi started and scored a try as Northampton beat Saracens to win the Premiership.[6]