I Think I'm in Love With You - Chart Performance

Chart Performance

"I Think I'm In Love With You" was more up tempo than Simpson's previous singles and became a moderate hit. In the United States, the single debuted at number sixty-three on the Billboard Hot 100, on the issue dated July 1, 2000. Due largely on the strength of its radio airplay, the song peaked at number twenty-one in its seventh week and stayed on the chart for sixteen weeks. The single reached number five on Billboard Pop Songs and stayed on chart for twenty-two weeks. "I Think I'm In Love With You" was her first top-five on the chart. Also achieved success on the Adult Contemporary and Rhythmic Top 40 charts.

In Canada, "I Think I'm In Love With You" reached the top-twenty, peaking at number fourteen. It became her second top-twenty in that country. The song also reached number two on the Canada RPM Singles Chart and was her highest peak at the time. The song stayed on the chart for twenty weeks. In Australia, the single debuted at number thirty on the ARIA Charts during the week of June 25, 2000. Five weeks later, it reached number ten and was her second top-ten there. The single stayed on the chart for fifteen weeks. It was later certified gold by Australian Recording Industry Association (ARIA), denoting shipments of 35,000 units within the country. In New Zealand, the song debuted at number thirty-three on the issue of August 6, 2000. In its third week on the chart, the single peaked at number twenty.

In United Kingdom, "I Think I'm In Love With You" debuted at number fifteen on the UK Singles Chart for the week of July 15, 2000, and stayed on the chart for seven weeks. It became her second top-twenty single there. In Switzerland, the single debuted at number sixty-one on the issue dated June 25, 2000. In the next week peaked at number forty-one and stayed on the chart for twelve weeks. The single peaked at number three on the Ultratip chart of Belgium's Wallonia region, and number thirty-six on the Belgium Flanders Ultratop 50 chart. It also reached number thirty in Italy. "I Think I'm In Love With You" peaked at number thirty-one on the European Hot 100 Singles chart, as compiled by Billboard.