Masaga, 23, made his All Blacks debut against Italy in Christchurch earlier this year.
He has been a member of the Chiefs team since 2006, has played 42 Super 14 rugby games and scored 21 tries.
Curragh said it was pleasing to sign a player of Masaga's quality.
"To attract a player of Lelia's calibre is fantastic and proves that the Bay can provide the right environment for players to make the All Blacks."
Masaga played his Air New Zealand Cup rugby for Counties Manukau this season.