Sergent, who went into the event as favourite, took the silver medal a whisker behind flying Australian Jack Bobridge in the men's individual pursuit.
Invercargill's Eddie Dawkins won a bronze in the men's time trial earlier in the track-cycling session.
They were New Zealand's first medals of the Games but there will be disappointment that neither was gold.
Sergent (22) matched his silver from the world championships in Denmark after a thrilling final at the Indira Ghandi Sports Complex.
Bobridge jumped to the front and managed to hold off the hard-finishing Sergent.
His time of 4min 17.495sec was 0.338sec slower than Bobridge, who led by nearly 1.5sec at the midway point of the race, before the New Zealander began a late charge.
He steadily ate into the margin but not quickly enough against the rising Australian star, whom cycling legend Lance Armstrong recently described as "the real deal".
Dawkins was disappointed with his performance in the 1km time trial, having been affected by a technical fault.
His handlebars were found to be out of alignment, which prompted a change only minutes before he took to the start line.
It meant he lacked control during his ride, which is probably why he clipped a small advertising marker in the final lap.
Australia and New Zealand also squared off for the bronze medal in the 400m individual pursuit, with Kiwi Sam Bewley dipping out to Michael Hepburn.
Earlier, Dunedin's Alison Shanks finished just over a second outside a medal when placed sixth in the 500m time trial.
The event is regarded as a warm-up for her specialist individual pursuit event, which is scheduled to be held on Friday.
