Minhwan of FTIsland and Yulhee, a former member of Laboum, are to get married in 2018.
Minhwan made the announcement through his social media account Thursday, by posting a lengthy letter to his fans.
"(My girlfriend and I) plan on bearing the fruit of our relationship," the post read. "After coming to the life decision of marriage, I am thankful for the congratulations that I have received from so many."
After the post was updated, his management agency FNC Entertainment confirmed the marriage plan with an official announcement, saying "the wedding will take place this year."
The K-pop couple confirmed their relationship last September, after Yulhee posted several photos of her with Minhwan on her social media accounts, with a caption that read, "I don't want to let you go."
Yulhee left Laboum last November, saying that she went through "psychologically difficult times."