The 31-year-old, who has four caps for the All Blacks, was most recently with Western Force in Super Rugby.
"Alby has vast experience so we're looking forward to welcoming him into our environment," head coach Mark Tainton told the club website.
"He's a good communicator and has performed consistently at the highest level during his career."
Bristol have signed New Zealand international scrum-half Alby Mathewson on a deal until the end of the season.