Niculae started his career with Dinamo Bucureşti, progressing through their youth system to the first team squad. He made his first team debut in 1996 while he was still 15 years old and finished his time at the club having scored 44 goals in 100 Divizia A appearances. He joined Primeira Liga club Sporting CP in 2001 after signing for a reported transfer fee of $3,000,000. However, the actual transfer fee is believed to be around $4,500,000. His spell in Portugal is marked by many injuries netting only 14 goals in 59 league appearances, before leaving the club in 2005. He subsequently played for Standard Liège, Mainz 05 and Inverness, before returning to Dinamo in July 2008. Most of his four-year second spell for Dinamo, he activated as team captain until his departure to Vaslui in July 2012.