"Curious" was written by Hayley Kiyoko with Lisa Vitale, Brandon Colbein, Jakob Hazell and Svante Halldin. The track was produced by songwriting duo Jack & Coke, which consists of co-writers Hazell and Halldin. Describing herself as very selective when it comes to choosing her collaborators, Kiyoko described working with Jack & Coke as largely incidental because "there’s only a few guest producers on the album" and believes that both artists' strengths can be heard via their production throughout the track. "Curious" covers several of Kiyoko's past relationships with women, as she openly identifies as gay, during which she wanted to clarify that their feelings for each other were genuine as opposed to simply fun. "Curious" is partially based on true events about Kiyoko's "dalliance with a girl on the down-low". Admitting that she shares a personal connection with every song she writes, Kiyoko revealed that "Curious" specifically pertains to "that feeling of learning self-respect and ... walk away from a game". The singer believes any listener would find the situation addressed in the song relatable, claiming everyone has encountered similar dilemmas "where someone's playing games ... In the dating game, the world is difficult, because people don't communicate, or they communicate but then their actions speak louder than words."
