The 33-year-old, who was out of contract after finishing up at Montpellier, had been rumoured to be staying in the Top 14, with Castres his likely destination.
Benetton head into their fixture with Connacht in Treviso on Saturday in the United Rugby Championship looking to end a three-match losing streak which has seen them hurtle down the table.
Lam's departure leaves the Hurricanes short of a left wing, with a potential return for former All Black Julian Savea gaining traction after a tweet by Ardie Savea.
Ben Lam will play his 50th and final game for the Hurricanes when they take on the Crusaders in Christchurch this Saturday.
Ben Lam has been in fine form for the Hurricanes over the last three years but the national selectors have never come calling. Now he's been lost to New Zealand rugby.
Hurricanes management has confirmed Ben Lam will be leaving the club to play in France in the Top 14 at the end of this Super Rugby season.
Hurricanes winger Ben Lam's second-half burst propelled the Hurricanes away from the Durban-visitors in their home opener at Sky Stadium.
All Blacks head coach Steve Hansen has cleared up questions regarding the omission of Hurricanes wing Ben Lam from the national squad to take on France next month.
Hurricanes winger Ben Lam has been a revelation this season, but looks unlikely to be in the All Black’s thinking for June. Scotty Stevenson discusses the reasons why, and what it says about how tough it is to make the team.
