The Proisir gelding was positive out of the gates for jockey Matthew Cameron to sit outside Lord Cosmos, with the pair setting a solid tempo throughout.
The Jamie Richards-trained runner looked to have the field beaten turning for home when he kicked clear by a length, however, Cameron asked his charge to improve and he duly responded, quickening late to grab Lord Cosmos on the line to win by a long head, with a further 5-1/2 lengths back to Canufeelit in third.
Brennan was pleased with her gelding's run, particularly the fight he showed in the closing stages.
"I thought halfway down the straight that Lord Cosmos was going to take it out, but he dug deep and put his head down and ears back. He has got a lovely big stride on him and Matt timed it right," she said.
"I have liked him for a while. I was quietly confident but you never know with two-year-olds having their first start.
"I was a little bit nervous, but I was a bit relieved when the favourite (Time Flies) was scratched this morning.
"He is still a bit green and has a bit to learn but he showed he has guts and grit. He is a lovely strong two-year-old."
Brennan said she will now wait and see how Zaher pulls up after the race before making any immediate plans with him.
"He has got his two-year-old win now so whether we put him out for a couple of weeks now and bring him back we will just let him tell us," she said.
"We will just see how he pulls up from this."
Meanwhile, Brennan is looking forward to lining up consistent gelding Packing Rockstar in the Geoff Brindley Memorial 1400 at Te Aroha on Saturday.
The Fastnet Rock six-year-old was runner-up in the Gr.3 Sweynesse Stakes (1215m) behind Tavi Mac last month before placing in a 1025m trial at Taupo.
While Brennan would have liked to have headed to the races with Packing Rockstar since then, she said inclement weather had put a stop to that.
"It is a while between runs, which isn't ideal, but through weather conditions we have had to scratch him a few times," she said.
"I was really happy with his trial, he relaxed nicely and hit the line well. He was supposed to run that week but we had to trial him instead.
"Whatever he does on Saturday he will benefit from and will be better next time."
Packing Rockstar has some big targets in the New Year, including the Gr.1 Railway (1200m) at Ellerslie on New Year's Day, a race he finished fourth in earlier this year.
"We will head the Railway-Telegraph route and hopefully we can get some results with him, he is so consistent and tries every time, that's all you can ask," Brennan said."He has been so close in a lot of those stakes races and it would be nice to pull one off at some stage over the summer."