Mendes and Cabello promoted the song with several televised performances, including on The Tonight Show Starring Jimmy Fallon and at the 2016 People's Choice Awards.

"I Know What You Did Last Summer" was written backstage spontaneously on one of Taylor Swift's The 1989 World Tour stops, in which Mendes was an opening act and Cabello was the surprise guest as part of the group Fifth Harmony.

[5] Mendes and Cabello performed the track again on The Tonight Show Starring Jimmy Fallon on January 4, 2016.

[6] Preceded by a performance of "Stitches", Mendes and Cabello sang "I Know What You Did Last Summer" at the 2016 People's Choice Awards.

[8] Mendes and Cabello performed the track again at the Radio City Music Hall on March 5, 2016, in New York.

[9] Mendes and Cabello also performed the track while on the 2015 iHeartRadio Jingle Ball tour in December, on the following dates: 1, 4, 11, 16, 18 and 19.