Dix returned to national competition with an appearance at the 2010 USA Indoor Track and Field Championships. He took fourth place in the final and set a new 60 m indoor best of 6.58 seconds. Event winner Ivory Williams was disqualified after testing positive for marijuana and Dix was upgraded to third. He opened his outdoor season at the Seminole Twilight meet in May, recording 9.98 seconds in the 100 m and 19.89 seconds for the 200 m. He began to participate in Diamond League meetings, competing on the European circuit for the first time. He beat Wallace Spearmon at the Golden Gala's 200 m race, breaking Michael Johnson's meet record. He also took to the national stage, winning the 100 m and finishing as the 200 m runner-up at the 2010 USA Outdoor Track and Field Championships. A week later, Dix beat Tyson Gay at the Prefontaine Classic for another meet record of 19.72 seconds. In August at a meet in Nottwil, Switzerland, Dix ran a new personal best of 9.88 seconds, finishing second behind Nesta Carter who also set a new personal best of 9.86 seconds. An injury at the London Grand Prix brought an end to his season.