[3] Heffron made his professional debut on 4 September 2010, scoring a second-round knockout (KO) victory against Torsten Roos at the Bekkerveld Festival in Heerlen, Netherlands.

[4] After compiling a record of 19–0 (15 KOs), he defeated Andrew Robinson via sixth-round technical knockout (TKO) on 9 June 2018 at the Manchester Arena, capturing the vacant WBC International middleweight title.

[5] Following a fourth-round TKO victory against Aryee Ayittey in October,[6] Heffron returned to the Manchester Arena to face former British super-welterweight champion Liam Williams for the vacant British middleweight title on 22 December, serving as part of the undercard for Josh Warrington's world title defence against Carl Frampton.

In the tenth, he was caught with a punch which prompted Williams to launch a sustained attack and force referee Howard Foster to issue a standing eight count.

[8] Heffron won the British and Commonwealth super middleweight titles by stopping defending champion Lennox Clarke in the fifth round of their contest at the Copper Box Arena in London on 16 July 2022.