Balchin (20) finished the 10km course in 31min 4sec, just 6sec ahead of his nearest rival, Callan Moody (Ariki).
"We were side by side for pretty much the whole race and with 500m to go, I picked up the pace a bit and a gap formed and it stayed like that until the end," Balchin said.
Otago was fielding a strong team and had a good chance at the national road race championships later this month in Wellington, he said.
"The Otago team managed to win the cross-country title last month, for the first time in 53 years, so we're hoping to win the road race as well and make it a double."
Balchin said he always enjoyed the Clyde to Alexandra race and it generally produced fast times.
Competing for the first time since April, Hill City runner Shireen Crumpton (40) took the open women's title in a time of 36min 14sec.
"I've got a long-standing Achilles problem and I'll be having surgery on that in December," she said.
Although it was not her fastest time in the race, which she has won several times, she was happy with the performance.
"I probably went out a bit quick at the start and the wheels fell off near the end, but it was a good race, considering it's my first one since April."
In a fortnight, Crumpton heads to New Caledonia for the Noumea marathon. She won that event last year.
More than 330 runners and walkers took part in the 43rd Clyde to Alexandra road race, with the temperature during the race topping 18degC.
The event is organised and hosted by the Alexandra Harrier and Walkers Club and transponders were used for the first time this year to record the race times.
