The pair teamed up last season to guide the former battler into the playoffs for the first time since 2002.
The Grizzlies were beaten 10-8 in a tense semifinal by Taieri. While it was disappointing to bow out at that stage, it was a big turnaround for a team which had to play in a promotion-regelation game just two years earlier.
Club president Craig Anderson was delighted the men had decided to return for another stint.
Moeahu will be in his fifth season in a head coaching role with the team. He had hopes of securing a coaching role with the Otago team but will continue his impressive work at club level.
The former halfback played 223 games for Green Island from 1995 to 2015 before switching to coaching.
He has been instrumental in the turnaround at Miller Park.
Vaafusuaga will be in his second season with the club. He had a long playing career, mostly for Taieri but also played for Green Island when Taieri dropped out of the premier grade.
Green Island will be without powerhouse No8 Dylan Nel, who has signed with the Chiefs and will be a big loss.
The club will field a premier colts team next season. Anderson said that was a first ''in quite a while''. That team will be coached by Mike Robertson, who was previously coach at the Dunedin club.