On 21 January 2000, Niculae was called up to the Romania national team for the first time. On 2 February, he was in the start-up team against Latvia, counting his debut for the senior squad, at only 18 years old. Same as he did while playing for Romania U-21, Niculae marked his debut for the senior squad with a goal, netting Romania's second in a 2–0 win. Despite he scored 20 goals for Dinamo in the 1999–00 season, Niculae was not included by Emerich Ienei in the preliminary squad for UEFA Euro 2000.