Club president Bernard Pontneau was quoted by French broadcaster RMC Sport confirming the move after next year's Rugby World Cup.
Rumours have abounded as to the Highlanders and All Blacks outside back's future in recent times, many having linked him to Pau.
"We would have liked to have had this sorted earlier than this." Pontneau reportedly said.
"He is is a great player, who will bring a lot to the team.
"He will have a big impact with the group and our young players will be able to learn from a player of his magnitude. He'll make them move faster."
Smith (32) has 76 test caps to his name, having scored 33 tries since his debut in 2009.
He has been a regular in the side over the past six seasons and has been used both on the wing and at fullback.
Meanwhile the same report suggested Hurricanes and All Blacks loose forward Ardie Savea will not join the club.