During his tenure as a trainee with Happy Face Entertainment (now Dreamcatcher Company), he was a contestant on the reality survival series Produce 101 and Mix Nine, where he competed to debut in an idol group.

He found success in the latter and ranked number one in the competition, but the group never materialized due to failed contract negotiations between the show creator YG Entertainment and the artists' respective agencies.

[7][8] He later joined Happy Face Entertainment and participated in the second season of Mnet's survival reality series Produce 101 (2017), where contestants competed to become a member of the boy group Wanna One.

[14] Woo, along with fellow HF Music Company trainees and Produce 101 contestants Park Woo-dam, Jung Won-cheol, and Jo Yong-geun, released a special single entitled "Be the Light" on June 26.

[17] He remained at the summit every week until the penultimate episode upon being overtaken by fellow contestant Kim Hyo-jin, but Woo finished in first placed at the end of the competition.

[19] CEO of the company Yang Hyun-suk later presented the members' agencies with a three-year contract and following failed negotiations, the debut of the group was canceled.

[21] The suit was dropped the following April, with a representative of Woo stating that they had accepted the production team's sincere apology and that the two sides had amicably settled the dispute.

[22] Woo took part in the eighth season of the rap competition series Show Me the Money (2019), but failed to move beyond the initial preliminary round.

[25] Happy Face Entertainment announced the group HNB (Happyface Next Boys) consisting of Woo and other trainees with the agency, and they held a fan meeting in May 2018.