Hammett coached the Hurricanes from 2011-2014, compiling a record of 29 wins, two draws and 33 losses, before joining the Cardiff Blues as their Director of Rugby.
However, six months into a three year contract, he was released at his request to return home to New Zealand.
The former All Blacks hooker has also signed on as an assistant coach for the Tasman Makos in the 2016 National Provincial Championship - a role which is unlikely to clash with the Sunwolves role, as the Sunwolves are a big outside shot to make the Super Rugby playoffs.
Meanwhile, Super Rugby title-winning coach Jamie Joseph is reported to have agreed to coach the Japan national side, replacing new England boss Eddie Jones.
His hiring is expected to be officially revealed later in the week.
Sunwolves squad: Ryuhei Arita, Timothy Bond, Derek Carpenter, Andrew Durutalo, Ziun Gu, Shohei Hirano, Atsushi Hiwasa, Shota Horie, Yoshiya Hosoda, Keita Inagaki, Daisuke Inoue, Shinnosuke Kakinaga, Takeshi Kizu, Yamamoto Koki, Faatiga Lemalu, Tomas Leonardi, Amanaki Lotoahea, Shinya Makabe, Paea Mifi Poseti, Masataka Mikami, Liaki Moli, Tsuyoshi Murata, Hitoshi Ono, Tusi Pisi, Eddie Quirk, Yusataka Sasakura, John Stewart, Yu Tamura, Harumichi Tatekawa, Riaan Viljoen, Akihito Yamada, Ryohei Yamanaka, Hajime Yamashita, Yuki Yatomi
