The backrow man joins the club following a successful trial period, having been a free agent after leaving English side Doncaster at the conclusion of the 2019/20 season.
Capped 13 times by the Ikale Tahi, Lokotui made his international debut against Japan in 2017 and was part of Tonga's 31-man squad for the 2019 Rugby World Cup.
Prior to linking up with the Warriors, the flanker had represented Counties Manakau with distinction in New Zealand's ITM (now Mitre10) Cup.
The Longoteme-born man scored six tries in 18 appearances for the Steelers, before heading north for an eye-catching 12-game stint with Doncaster in the English Championship.