Northern Ireland’s three-game winning run in their Euro 2016 qualifiers ended as Romania won in Bucharest to go top of Group F.
Full-back Paul Papp scored both goals, firing into the top corner in the 73rd minute and stealing in to convert a back-post header.
Chris Brunt went close early on but Alexandru Chipciu hit the bar and Bogdan Stancu missed from close range.
Northern Ireland slipped to second in the group, one point behind Romania.
Romania began the first European Championship qualifying meeting between the sides hoping to avoid a repeat of their only previous competitive home match with Northern Ireland, a World Cup qualifier in October, 1985, which they lost 1-0.
Michael O’Neill’s Northern Ireland went into the game full of confidence but without several injured players, including skipper Steven Davis.
Anghel Iordanescu was beginning his third spell as Romania coach following the departure of Victor Piturca, who left to take up a lucrative deal with Saudi Arabian side Ittihad last month.
The hosts, also without several first-choice regulars, began brightly and a bicycle kick by out-of-favour Tottenham defender Vlad Chiriches was gathered by Roy Carroll.