On 27 July 2010, Heffernan won the bronze medal in the 2010 European Athletics Championships in the 20 kilometres walk, posting a time of 1:21:00 (achieved retrospectively in 2014 after Russian Stanislav Emelyanov was found to have committed an anti-doping violation).

He also finished 4th in the 50km walk in a national record time of 3:45:30, a notable achievement just three days after the 20 km event.

[3] In early 2015, it was revealed that a number of Russian male and female champion racewalkers were under investigation for doping violations including the winner of the 50 km walk in London, Sergey Kirdyapkin.

On 24 March 2016, the court of Arbitration for Sport favoured the IAAF and Heffernan was upgraded to Olympic Bronze.

[12][13] In November 2022, Heffernan was announced as performance coach of the Cork senior footballers, working under the management of John Cleary.