Barry Slattery joined Kildare County during the 2006 pre season from Kilkenny City F.C.. The midfielder made 15 appearances starting nine games and coming on as a substitute in six others. Slattery was also a member of the Kildare County Under-21 team that was defeated by Cork City F.C. in the final of the Enda McGuill Cup in 2006. He impressed in his first season at the club and was offered a new contract by manager John Ryan for the 2007 season. However Slattery signed for the St. Patricks Athletic Under-21 team before the 2007 season started. Slattery rejoined Kildare County for the 2008 season.