On Sunday (06Sep20), the actor, 35, announced that he had proposed to his partner, writing alongside a sweet selfie of the couple, "She said yeah."
In the snap, "The Royals" star, 31, is seen cosying up to her fiance while showing off her new ring.
Park has yet to share the news on her own social media pages although she did post a photo from her and Lafferty's romantic getaway to Palm Springs, California.
"Hello," she penned - but fans were quick to acknowledge the engagement news in the comments.
"Congrats to you girl!! Can't wait to see what this new chapter of your life looks like! So happy that you are happy," one fan shared, while another added, "congrats on your engagement."
The couple has been together since at least 2018 when Park posted a photo with Lafferty and his "One Tree Hill" co-star Stephen Colletti.