Cullen is a potential romance option for a female Inquisitor in Dragon Age: Inquisition, although only for humans or elves. He is also one of the few romance options whose romance can be initiated before the completion of his personal quest.
His romance can be initiated shortly after arrival at Skyhold by the Inquisitor, who (during a very awkward confrontation on the battlements that results from the Inquisitor asking if he has "time to talk") confesses their feelings towards him. Provided that the Inquisitor fits Cullen's specifications (female and human/elf), the feelings are mutual and they share their first kiss. Cullen says later that he'd been wanting to kiss the Inquisitor "longer than he should admit".
After a mage Inquisitor encourages Cullen to continue to refuse lyrium, he can express regret for his attitudes in the previous game and state that, "The way that I saw mages...I'm not sure I would have cared about you. And the thought of that sickens me."
As with all other romanceable characters, if the inquisitor romances Cullen, two Orlesian nobles in the throne room will comment on the romance at each progression.