 Iraola was born in Usurbil, Gipuzkoa.A product of Athletic Bilbao's youth system at Lezama after joining from Antiguoko, he made his debut with the first team in the 2003–04 season, becoming an instant first-choice while often taking penalties and free kicks.On 30 August 2003 he made his first La Liga appearance, starting in a 0–1 home loss against FC Barcelona, and his five goals in 30 appearances helped the team qualify for the UEFA Cup.