[2] Following his departure from U-KISS, Woo pursued a solo career in South Korea and Japan; he debuted as a soloist with his first single "Ride Along" in October 2018.

[4] His family has a creative background being that his mother was a fashion model in South Korea and his paternal uncle, Emmanuel Woo,[5] was an actor and classical opera singer in Germany.

In February 2009, Woo joined Arirang TV's[7] radio show Pops in Seoul as a host of segment "All About You" alongside co-host Kim Isak.

In December 2009, Woo with fellow U-KISS member Alexander released a single "Finally", which was composed by Brave Brothers.

In July 2010, Woo with U-KISS members Soohyun, Kibum, Kiseop and Dongho became a part of the drama I Am Legend,[8] acting as a rock band.

On October 12, Woo with U-KISS members Eli announced that they would have a collaboration with Japanese singer JAMOSA from Avex label for her single "Together".

[14] Woo alongside bandmates Soohyun, Eli and Kiseop participated in the drama KPOP The Ultimate Audition, having small cameo appearances in three episodes as a senior idol group to the main cast.

[15] Woo and Soohyun were selected to appear in the Korean adaptation of the musical Summer Snow alongside Super Junior's Sungmin, Supernova's Sungjae, SS501's Heo Young-saeng and FT Island's Seunghyun from April to June 2013.

[22] He debuted the song during his set at music festival KCON at its New York dates, fulfilling one of his dreams to perform at Madison Square Garden.

The duo promoted the single with a two-date concert tour in Los Angeles and San Francisco on August 24 to 25, and a music video released in November 6.

[25][26] Woo joined the Live From Home livestream charity concert held on May 23, where proceeds benefitted the CDC Foundation's crisis fund for the COVID-19 pandemic.

[27] Woo temporarily rejoined U-KISS as a duo with Soohyun as part of a special throwback-themed "Guilty Pleasures" concert from SBS and its variety show MMTG in October 2020.

[29] In March 2021, it was announced that survival horror video game Dead by Daylight would feature a K-pop-themed killer called "The Trickster;" Woo was brought on as a consultant for the character's portrayal.

[32] Woo will make his Broadway debut with the K-Pop inspired musical KPOP, which began previews on October 13, 2022, and opened on November 20 in New York City.