Jung Hae-in made his official acting debut in the 2014 TV Chosun series Hundred Year Bride. Later in 2014, he became part of the tvN sageuk drama Three Musketeers. In 2016, he made a cameo appearance in the hit tvN fantasy romantic drama The Lonely Shining Goblin as the first love of Kim Go-eun’s character. In 2017, he was included in the main cast of the SBS series While You Were Sleeping, in which he was nominated for an Excellence Award at the 25th SBS Drama Awards. He next appeared in the tvN series Smart Prison Living, which won him the Most Popular Actor award at the 54th Baeksang Arts Awards. In 2018, Jung Hae-in was cast in his first leading role in the JTBC romantic drama Pretty Noona Who Buys Me Food. He bagged an Excellence Award at the 2018 APAN Star Awards for his performance in the series. In 2019, he headlined the MBC romantic drama One Spring Night, which earned him a Top Excellence Award at the MBC Drama Awards. Also in 2019, he took home the Best New Actor trophy at the 56th Grand Bell Awards for the movie Tune in for Love.
Jung Hae-in is a descendant of the prominent Silhak philosopher Jeong Yakyong. He enlisted for his mandatory military service when he was 21 years old.