Kwak debuted as an actor in the 2014 drama Glorious Day. His first major role was in the film 2014 Night Flight. He then appeared in the music drama, Persevere, Goo Hae-Ra.
On October 1, 2015, Starhaus Entertainment launched the project group One O One, releasing their debut single “Love You”. The group consists of Kwak along with fellow Starhaus actors Ahn Hyo-Seop, Song Won-suk, and Kwon Do-Kyun.
He then starred in the daily drama All is Well, and joined the reality show We Got Married where he was paired with actress Kim So-Yeon.
In 2016, Kwak starred in his first historical drama Mirror of the Witch. He received his first major role in SBS’s 2016 drama Second To Last Love, which won him the New Star Award at SBS Drama Awards.
In 2017, he starred in tvN’s fantasy-romance drama Chicago Typewriter as Yoo Ah-in’s rival. He also made a special appearance in KBS’s romantic comedy-drama Fight for My Way.
In 2018, Kwak appeared in the thriller film The Witness, and also in the romance thriller drama Four Men, a prequel to 2017’s Man to Man.