On October 28, 2016, she was revealed as the second member of LOONA. Her solo single album, titled "HyunJin", was released on November 17.
2017: Debut with LOONA 1/3, MIXNINE
She debuted as a member of the group's first sub-unit, LOONA 1/3, on March 7, 2017 with the mini album Love & Live.
In October, Hyunjin, alongside fellow members HeeJin and HaSeul, became contestants on the survival show MIXNINE, representing their agency and group. She was eliminated in the finale after ranking 11th place.
2018: Debut with LOONA
On August 20, 2018, LOONA debuted as a full twelve-member group with their first mini album + +.