Mendes was set to record his vocals on a day off during his UK tour; however, Watt blew the microphone, which delayed things. Much to Mendes' annoyance, this meant he had to lay them down just before a run of four nights at London's O2 Arena, just when he had been planning to rest his voice. Watt told Billboard
he thinks Mendes' "amazing raspy tone" was because he was so cross.
Having recorded his vocals, Mendes then FaceTimed Cabello and started tweaking the lyrics with her. The first time they were actually in the studio together was a fortnight before the song came out. "Señorita" was already being mixed when Cabello came up with, "You say we're just friends but friends don't know the way they taste." She insisted on the lyric being there, so Mendes had to come in and re-sing his harmonies just for that line.