Filan was born on July 5, 1979 to Peter and Mae Filan, and grew up in Sligo, a busy commercial town in the northwest of Ireland. The youngest of seven children, he has three brothers and three sisters: Finbarr, Peter Jr, Yvonne, Liam, Denise and Mairead. His parents owned a diner in Sligo named Carlton Cafe located on Castle Street and Shane used to work there as a waiter from a very early age.
Filan attended Summer hill College, a Catholic school, with Kian Egan and Mark Feehily. All three of them participated in a school production of Grease when they were about 12. The Hawkswell Theatre became a significant part of their careers. Filan was a fan of Michael Jackson as a child, and claimed the singer inspired him to pursue a career in music