
"I Think I'm in Love with You" was the first of Simpson's videos to be set to an up-tempo beat. "I Think I'm in Love with You" peaked at number 31 on the European Hot 100 Singles chart, as compiled by Billboard. The single peaked at number three on the Ultratip chart of Belgium's Wallonia region, and number 36 on the Belgium Flanders Ultratop 50 chart. In the next week it peaked at number 41 and stayed on the chart for 12 weeks. In Switzerland, the single debuted at number 61 on the issue dated June 25, 2000. It became her second top 20 single there. In United Kingdom, "I Think I'm in Love with You" debuted at number 15 on the UK Singles Chart in the week of July 15, 2000, and stayed on the chart for seven weeks. In its third week on the chart, the single peaked at number 20. In New Zealand, the song debuted at number 33 on the issue of August 6, 2000. It was later certified gold by the Australian Recording Industry Association (ARIA), denoting shipments of 35,000 units within the country. The single stayed on the chart for 15 weeks. Five weeks later, it reached number 10 and was her second top 10 there. In Australia, the single debuted at number 30 on the ARIA Charts during the week of June 25, 2000. The song stayed on the chart for 20 weeks. The song also reached number two on the Canada RPM singles chart and was her highest peak at the time. It became her second top 20 hit in that country. In Canada, "I Think I'm in Love with You" reached the top 20, peaking at number 14. As the date, "I Think I'm in Love with You" sold 20,000 physical copies and has sold over 316,000 paid digital downloads according to Nielsen SoundScan. Also achieved success on the Adult Contemporary and Rhythmic Top 40 charts.

"I Think I'm in Love with You" was her first top five on the chart. The single reached number five on Billboard Pop Songs and stayed on chart for 22 weeks. Due largely on the strength of its radio airplay, the song peaked at number 21 in its seventh week and stayed on the chart for 16 weeks. In the United States, the single debuted at number 63 on the Billboard Hot 100, on the issue dated July 1, 2000. "I Think I'm in Love with You" was more up-tempo than Simpson's previous singles and became a moderate hit. The song is written in the key of A major, with a chord progression of A–E/A–A–E-D, and the song is set in common time with a tempo of 106 beats per minute. The song samples the signature opening guitar-based melody line of John Mellencamp's 1982 hit Jack & Diane. "I Think I'm in Love with You" is a dance-pop song, with a length of three minutes and 35 seconds. Problems playing this file? See media help. It is 22 seconds longer than the original album version. A radio / single mix of the song was also released with a slightly longer outro. Simpson recorded a Spanish version of the song titled "Tal vez Es Amor". Los Angeles radio station KBIG-104 produced a mixed version of "I Think I'm in Love with You" with a few samples of "Jack and Diane" lyrics and the same ending as the original version. In the United States, it peaked at number 21 on the Billboard Hot 100. The single reached the top 10 in Australia and Canada and the top 20 in Iceland, New Zealand, and the United Kingdom. It contains a sample of singer-songwriter John Mellencamp's " Jack & Diane" (1982) and was released as the album's third and final single in mid-2000 in Japan, it was issued as the album's second single in February 2000.

" I Think I'm in Love with You" is a song written and produced by Cory Rooney and Dan Shea for Jessica Simpson's 1999 debut album, Sweet Kisses.
