McFadden was educated at St Eunan's College in Letterkenny. In 2000, he was part of the team that won the school's third McLarnon Cup, the first win since 1979. That 2000 final victory over St Columb's of Derry at Casement Park has been described as "arguably the match that catapulted him to people's attention outside of Donegal". He scored a late goal to give the College victory by a scoreline of 1–11 to 1–9, 1–8 of which McFadden scored himself. While completing his Leaving Certificate, McFadden was part of the under-17 Ireland international rules football team. His words of advice also helped the College to reclaim the McLarnon Cup in 2007, and to go on to compete in the All-Ireland "B" Colleges Final, which they subsequently lost.