Jeong Se-woon first appeared in 2013 as a contestant in the third season of K-pop Star. He passed the first round of auditions with a performance of his original song titled "Mom, Wait a Minute" (Hangul: 엄마 잠깐만). One of the judges in the show, founder and former JYP Entertainment CEO Park Jin-young, praised the musical form of the song and had likened him to Akdong Musician, who were the winners of the second season of K-pop Star. Starting on the third round, he competed in the show as part of the duo called Something (Hangul: 썸띵) with fellow contestant Kim Ah-hyeon. The duo reached the finals but were eliminated during the first round of live performances. Three months after the show, Se-woon signed a contract with Starship Entertainment.In 2017, he participated in Produce 101 Season 2 to represent Starship Entertainment with fellow trainee Lee Gwang-hyun. He became part of the Top 20 but was eliminated during the finale, after ranking 12th overall with 769,859 votes. After the show, on August 1, it was reported that he had started preparing for his solo debut.