In 2010 Thompson kept her amateur status for the first half of the year. As an amateur, she played in the Women's Australian Open, where she finished T16 (+3), 12 strokes behind the winner, Yani Tseng. She made the cut at the 2010 Kraft Nabisco Championship, finishing T24, +2 (74-72-73-71=290), 15 shots behind winner, Yani Tseng. She also won the 2009 Verizon Junior Heritage after a sudden-death playoff with Laetitia Beck. She represented the winning United States team in the Curtis Cup competition and went undefeated, winning four matches and tying in a fifth. She turned pro the next week, stating she believed her game was ready to make the jump to the LPGA Tour.