"We feel very good about acquiring Smush," coach Pat Riley said in a statement. "He brings size, shooting and defense to our backcourt. He has been improving every year, and we feel that this could be his best year yet."
Parker helped guide the Los Angeles Lakers to the playoffs in each of his two seasons as their starting point guard. They were over the salary cap and didn't try to re-sign him.
He played in all 164 games the past two seasons, averaging 11.3 points, 3.2 assists, 1.6 steals and 32 minutes.
Parker went undrafted in 2002 and was with Cleveland, Atlanta, Charlotte, Detroit and Phoenix before joining the Lakers.
"We are excited to bring Smush to Miami," Heat general manager Randy Pfund said. "He's a talented young player who brings good size and athleticism to our point-guard position. Smush has been the starting point guard of a playoff team the past two seasons, and we believe he has his best years ahead of him."