Born in Thessaloniki, Lagos started his professional football career with Iraklis in 2002. Having made 76 appearances for the club, he became one of the most important players in qualifying for Europe during the 2005–06 season.
Lagos was a target of many big Greek clubs, Olympiacos, Panathinaikos and PAOK, in the end Lagos signed with AEK Athens for €1 million and was transferred from Iraklis in 2006. Lagos scored his first goal for AEK Athens against Atromitos in a 4-0 home win. In his first season at AEK Lagos started his career with AEK brightly before suffering a serious injury on his right leg in 2007, forcing him out of football for two years and made his come back near the end of the 2008-2009 season. Lagos' first game back from his injury was in a derby match against Panathinaikos. Lagos is now a regular in the AEK Athens starting line-up, being played as a left wingback.
In 2010, Lagos renewed his contract with the club signing a new three-year deal witch will last him at the club until 2013. Lagos scored 2 goals against Larissa which lead AEK winning 2-3. Lagos again suffered a knee injury against R.S.C. Anderlecht which forced him out of football for 3 months. Lagos made his comeback against Ergotelis where the match finished 1-1