After participating in the Mnet program Hot Blood in 2008, Im Seul-ong was chosen to become part of the four-member group 2AM. They officially debuted in July of that year with the single This Song. In 2010, Im Seul-ong made his acting debut in the MBC romantic comedy Personal Taste, which earned him a Best New Actor nomination at the MBC Drama Awards. That same year, he collaborated with IU for the hit pop ballad Nagging, which was used as a theme song for the second season of the MBC reality show We Got Married. In 2012, he starred in the movie 26 Years, which won him Best New Actor at the 1st Marie Claire Film & Music Festival. In 2013, he joined KBS2’s fugitive-thriller sageuk Mandate of Heaven. In 2015, he acted alongside Choi Woo-shik and UEE in tvN’s Ho-gu’s Love, which scored him a Baeksang Most Popular Actor for TV nomination.

Im Seul-ong enlisted for his mandatory military service as an active-duty soldier in November 2017. However, his status was changed to reservist due to his various medical conditions. He was eventually discharged in October 2019. In August 2020, he got involved in a car accident in Seoul that resulted in the death of a pedestrian.