Heffernan scored 27 goals in 61 appearances in two seasons at Kilmarnock but manager Allan Johnston has decided he has enough up front with Kris Boyd, Mark Stewart and William Gros.
The 31-year-old Irishman, who has also played for Doncaster and Sheffield Wednesday, made a surprise move to Easter Road last night and has signed a contract until the end of the 2014-15 season.
Heffernan told the Hibernian website: “I’m excited about starting the next chapter of my career at Hibernian; hopefully my time with the club will be successful.
“I spoke to both Michael [Nelson] and Tim [Clancy] about coming here and they both encouraged me to join.
“It’s a good club with big support – I saw that at the cup tie at Rugby Park last season – and I’m looking forward to playing for Hibs.”
Easter Road manager Pat Fenlon has now signed ten players this summer, with Heffernan competing with fellow new recruits James Collins and Rowan Vine for a place up front.
Fenlon said: “We’re delighted to be able to get Paul – the situation concerning his arrival developed very late on. He is a good, experienced player and his goalscoring record is very good. He knows the league inside out and he’s different to what we have. Paul comes in with a good pedigree and hopefully he will bring both goals and experience to the team.”
Fenlon’s other signing, 21-year-old Zoubir, joins from Ligue 2 side FC Istres on loan for the season following a successful trial this week, subject to international clearance.
Meanwhile, the Scottish Football Association has clarified why the transfer window will close earlier in Scotland compared to some other countries.
The deadline north of the border is tonight at 11pm, while clubs in England, for example, have until 11pm on Monday to negotiate deals on transfers. An SFA spokesman explained: “The window closes tomorrow because Saturday is a working day for our registration department.
“Uefa sent round a circular on 21 June saying that the deadline can be moved to the first working day after 31 August. Saturday is a working day for us and there are something like ten other associations who are all closing on the 31st as well.”