Kim Jae-won made his acting debut in 2021 with a lead role in the Philippine mini-series Love From Home. He next starred in the web dramas Romanced and Sea Village Cloud Pension, which were released in 2021 and 2022, respectively. He then played the young counterpart of Cha Seung-won’s character in the 2022 tvN series Our Blues. In December of the same year, he acted alongside Shin Eun-soo in the KBS drama special Like Otters. In 2023, he joined the main cast of the tvN action comedy Stealer: The Treasure Keeper.