The world number one and reigning Australian Open champion took the match 7-5 6-1 but accused her beaten opponent of being too loud on court, even of speaking to the match umpire.
Wozniacki has described Niculescu as "a player that tries to get into your head".
"I just tried to let the umpire know that he needed to pay attention to her grunting because she will hit the ball and two seconds later when the ball is on my side and I am right about to hit, she will start grunting and make a noise.
"She will change the grunt according to what she feels like", added Wozniacki.
Under tennis rules, umpires are allowed to act on grunting if it is deemed to affect an opponent through an intentional act.
"It is disturbing. It is in the rules that they are not supposed to do that so I was just making sure that the umpire was paying attention to that.
"She stopped doing that after."
Back to number one
Wozniacki returned to number one in the world in the women's game after winning her first grand slam title in Melbourne last month.
Niculescu, who got by Maria Sharapova in Qatar in round one, has defended her on-court style.
"That was very bad from Wozniacki - I have never heard a number one talk like that," she commented.
"I am really disappointed by what she said and I think she gives herself too much importance. I did not want to get in her head - this is just how I play."