Heffernan will join the Mariners after a stellar season at the Victorian NPL side, which qualified for the FFA Cup quarter-finals earlier this week when it beat Sydney United 58.
Heffernan was central to that result, scoring the FFA Cup's quickest goal when he opened the scoring against the Reds, after only 26 seconds.
The striker also impressed on trial at the Mariners, and scored a scarcely believable four minute hat-trick last month against Western Sydney Wanderers, in Coffs Harbour.
Mariners head coach Tony Walmsley said Heffernan, who was born in Manchester, brings versatility to his squad.
“Heff is a proven goalscorer over a long period of time and gives us a point of difference in attack that we currently don’t have,” Walmsley said.
“He gives us the opportunity to play two up front, added height in the front third and like we saw in our pre-season match against the Wanderers, he is a real goalscoring threat.
“We’ve had the added advantage of getting Dan into the camp environment on our trip to Coffs Harbour and his character has been well received by everyone, he’s a good fit for us.
It is a bit late in the day for Heffernan to sign his first professional contract, but the striker said he is excited to repay the faith the Mariners have shown in him.
He will join Mitch Austin and Roy O'Donovan as the squad's centre forwards.
“I’m so glad that Tony has shown faith in me,” Heffernan said.
“I’ve had people say to me that I could play full-time football but no one has actually taken the punt. Tony has seen something in me and gone with it so I am happy to be signing and thankful to Tony for the opportunity.
“There’s a good mix of players between the more experienced boys and the core of younger lads. Hutch filled me in on what the Mariners are about, as well as the area, it all seems like a really good fit for me.
“I’m looking forward to getting into the full-time environment to not only improve my fitness levels but also my sharpness and being able to learn from guys like Roy [O’Donovan] so I can bring my goal tally with me and improve on that.
