The former Gold Coast United, Wellington Phoenix and Central Coast playmaker was lured by coach John Aloisi, whose off-season recruitment policy has aimed to strengthen the club's attacking options.
The Heart, who scored 35 goals in 27 regular games last season, recently signed Croatian striker Josip Tadic and former Gold Coast United speedster Golgol Mebrahtu.
Aloisi, who played with Macallister at the Mariners, is excited by the 30-year-old's imminent arrival in Melbourne.
"Dylan is certainly a player who is going to add depth and support to our squad," said Aloisi.
"He's a different type of player to the attacking options we currently have up front in that he is a strong physical presence, who is also capable of taking up dangerous positions in the penalty box.
"He has a lot of experience to bring to the club. I'm looking forward to working with him. I know he is a great character and will certainly allow the younger guys to walk taller."
Macallister recently had a stint with Icelandic club Breiablik UBK, where he scored during a UEFA Champions League qualifier against Norwegian giants Rosenborg BK last season.