Prior to joining Brighton he made his full international debut for Ireland in August 2002. This came after having made 24 appearances for the under-21s and representing Ireland at every age group since turning 15. He also scored in a pre-season friendly for Arsenal against Stevenage. With Brighton, Barrett managed to attain 20 league starts, making a further ten appearances as a substitute, but again suffered a series of niggling injuries that held back his progress. At Brighton he also scored once against Sheffield United. Barrett was released from Highbury in May 2003, joining Coventry City on a three-year deal on 30 May. Barrett's injury problems continued while with the Sky Blues, where he made 32 league starts and made 23 substitute appearances in two seasons, scoring six goals. He joined Sheffield Wednesday on the loan deadline day in March 2005, where he scored once against Torquay United in six appearances. Barrett was told by manager Micky Adams that he was free to leave the club despite having one year remaining on his contract. Despite this he remained at Coventry, but, out of the first-team picture, went on loan to Scotland with Livingston. He played just six games for the club before suffering a season-ending knee injury. Signing a two-year with Scottish side Falkirk following his release from Coventry in August 2006, with the Bairns' medical staff satisfied with his rehabilitation after his serious knee injury the previous season. Once again though, Barrett suffered further injuries, requiring an operation on his knee in October 2006. He returned to action for the 2007–08 season, going on to sign a one-year contract extension in March 2008. After three operations and later being informed that his injury had been misdiagnosed, Barrett left Falkirk after manager John Hughes sat him down and told him he would never be the player he was before suffering his injuries. He was released from the club in January 2009. He had scored eight goals in 48 league games at the Falkirk Stadium. After going on trial with Heart of Midlothian, St Johnstone stepped in to sign Barrett after Hearts decided against handing him a deal. He was brought in to cover a spate of injuries amongst St Johnstones' forwards in February 2009. After nine appearances and one goal against Airdrieonians, Barrett was released by the club in the summer of 2009. Barrett returned to his native Ireland with Shamrock Rovers in August 2009. In his two seasons with the club, he amassed 21 appearances and scored once, but he still struggled with persistent injuries, holding him back from progressing and making a greater number of appearances.