Lee Shin-young debuted as an actor in the 2018 web series Just One Bite. He quickly gained recognition with his appearance in the hit romantic comedy Crash Landing on You, which aired on tvN from 2019 to 2020. This was followed by a leading role in the KBS2 short drama series How to Buy a Friend. His work in the series won him Best Actor in a One-Act/Special/Short Drama at the 2020 KBS Drama Awards. That same year, he was named Rookie Actor of the Year at the 15th Asia Model Awards.

In 2020, Lee Shin-young got embroiled in school bullying rumors, which were later cleared after one of the netizens who made the claims against the actor retracted his statements and issued a public apology.