[5] Barron made his first team debut against Brentford in a 2–0 League Cup first round win in August 2004 and played the full 90 minutes.
[8][9][10] Barron's injury problems continued into the 2005–06 season and he had to wait until December 2005 for his next appearance,[11] when he replaced Darren Currie after 87 minutes of a 1–1 Championship draw with Wolverhampton Wanderers.
[20] Barron made 16 appearances in 2008–09 and scored the first senior goal of his career in an FA Cup third round replay against Crewe Alexandra on 13 January 2009.
[22] In the 2009–10 season Barron made 29 appearances and won the first medal of his career when Millwall were promoted to the Championship after running out 1–0 victors against Swindon Town in the 2010 League One playoff final.
[37] Following his retirement, Barron joined Refuel Performance Management and continues to work alongside former Brentford teammate Richard Lee.