The 31-year-old completed a move from Kilmarnock the day before the transfer window closed.
Heffernan has admitted that he was surprised by the speed of the transfer.
"It all came out of the blue. I was at Kilmarnock and my agent spoke to the chairman, who said he was willing to let me go for free," Heffernan told BT Sport.
"My agent then spoke to Hibs and they were interested in bringing me here and that's how it happened. It was so quick. I was training as a Kilmarnock player on the Thursday and by the Friday I was having a medical at Hibs.
"But it's worked out well for me. I've signed a two-year deal at a bigger club and I'm delighted."
Heffernan scored 27 goals in 61 appearances for Kilmarnock.