Griffen Palmer wrote the song with frequent Shawn Mendes collaborator Geoff Warburton, and with Ben Simonetti (a member of Zac Brown-led trio Sir Rosevelt). He recalled to American Songwriter
they penned it in one day during a March 2019 songwriting session.
"I was carpooling to the session with Geoff and we were trying to get a jumpstart on the day by talking about ideas that we had," Palmer explained. "I had this idea kicking and pitched it to him in the car, saying 'well, what if we did a song called 'Second Guessing' and everyone thinks it's about having doubt or being unsure but then we flip the lyric and make it 'I haven't spent one second guessing'' and he was in on it right away. We kinda barged into the studio saying 'Ben, I think we've got it!' We started right away and there wasn't too much dilly-dallying."