The 33-year-old is the club's marquee player for the upcoming A-League season.
He has spent time in the Israeli Pro League, La Liga, the Championship during his career.
Hemed scored 28 goals during his first two Championship seasons when he was a Brighton player.
"When the opportunity [with the Phoenix] came up, we thought it was the best move for me as a player and for my family too," Hemed said of his move to Wellington.
"I've heard great things about the club and I know they had a special season last season."
Phoenix coach Ufuk Talay said: "Tomer is a highly skilled player with a pedigree as a goal scorer and creator.
"It's no secret the club was looking to improve its frontline with an experienced visa player, and Tomer provides what we ... think we need to improve on last season, someone who can convert our chances on goal and distribute to others."