The 27-year-old arrives at the Memorial Stadium early in the new year having caught the eye of head coach Richard Hill with his performances for the Highlanders in the Super 14.
Hill said: "He had an outstanding Super 14 where he consistently broke the advantage line and was always a threat with ball in hand. He will add real class and firepower to our back line.
"Neil also has strong leadership skills having captained Otago in their recent Air New Zealand Cup win over Northland.
"He is at his prime and will be integral to the continued development of Bristol Rugby."
Brew follows New Zealanders David Hill, the fly-half, and lock Sean Hohneck in signing for Bristol this summer.