Barnes turned professional in 2003 and joined the Nationwide Tour in 2004. His best finish in that venue came at the 2006 Oregon Classic when he lost to Cliff Kresge in a playoff. Barnes finished in the 25th spot on the 2008 Nationwide Tour money list which earned him his PGA Tour card for 2009.^{[citation needed]}

At the 2009 U.S. Open, Barnes set the 36-hole scoring record after shooting an 8-under 132 through the first two rounds in soft, rainy conditions. Early in the 3rd round, he became only the fourth player ever to reach double-digits under par.^[3] Barnes, however, suffered a collapse in the final round, shooting a 76 (+6) and placing in a tie for 2nd, two shots behind winner, Lucas Glover. The runner-up finish at the U.S. Open was his only top-25 finish in 2009, but he retained his tour card for 2010 by finishing 120th.^{[citation needed]}

In 2010, a string of top 10 finishes helped Barnes to comfortably keep his card, and he finished 43rd on the money list.^[4]

In January 2011 Barnes signed a contract with G/FORE, a golf company from fashion designer Mossimo Giannulli, to exclusively wear the G/FORE colored glove on the PGA Tour.^{[citation needed]}

After playing well enough to retain his card in 2011 and 2012, he slipped to 130th on the money list in 2013 and also missed the FedEx Cup playoffs (ranked 132). He played in the Web.com Tour Finals and finished 33rd to retain his PGA Tour card for 2014.^{[citation needed]}

At the 2016 Valero Texas Open, Barnes held the 54-hole lead/co-lead for only the third time in his PGA Tour career, after shooting a third round of 67 to lead by one stroke. He closed with a 74 in the final round and finished in a tie for 4th.^[5]

Barnes has now played in over 300 events on the PGA Tour without a victory.^[2]