Walsh's father was prominent in his local GAA club. He recalls his father coaching underage teams. As a young fella he played traditional music in one or two All Ireland Fleadhs.[3]
Walsh started for Donegal in their 2012 Ulster Senior Football Championship match against Cavan.[9] When Neil McGee sustained an injury after two minutes against Tyrone in the semi-final, Walsh came on as a substitute to help his team through to the final.[10][11] Walsh also made a substitute appearance against Cork in the All-Ireland semi-final, which Donegal won.[12]
^"Sam's World Tour of Donegal — Proud moment for Declan in Malin". 27 September 2012. Retrieved 27 September 2012. Declan Walsh was the proudest man in Ireland tonight at the country's most northerly GAA club as he carried the Sam Maguire into Malin. A huge crowd of enthusiastic supporters turned out to see the cup arrive in the town.