Radford (20), a student at the Sports Institute of Otago, won the title at the Caledonian ground yesterday with a score of 3111 points.
It was only Radford's third heptathlon.
She was runner-up in the Otago junior championships in 2005 with 2947 points and was third in the New Zealand junior championships with 3401 points in 2006.
Radford suffered from glandular fever and missed last season's athletics season, and is still finding her feet as she comes back into the sport.
Her best performances came in her favourite 100m hurdles in 17.84sec (505 points) and 200m in 29.14sec (544).
Radford gained personal best performances in the shot put (8.66m, 442 points) and javelin (21.76m, 322 points).
Radford is coached by Megan and Joan Merrilees, from whose stable came two other champions at the weekend.
Joan Merrilees was coach of the New Zealand team at the Commonwealth Youth championships in New Delhi last month.
Julius Keepa (Hill City) won the men's aged 17 to 19 decathlon with 3871 points.
His best performance was in the 100m (12.05sec, 641 points).
He also impressed by jumping 2.50m in his first pole vault.
John Gilmour (Hill City) won the boys aged 15 and 16 octathlon with 3950 points.
His best scores came in the 100m (11.50sec, 753), long jump (6.37m, 668) and shot put (10.89m, 539).
Hamish Finnie (Hill City) was runner-up with 3049 points.
His best performance was in the shot put with 13.69m for a score of 709 points.
Jarrod Adams (Hill City) won the men's decathlon with 4193 points.
His best scores came in the 100m (12.16sec, 620), shot put (10.39m, 509), 400m (53.09sec, 678), and 1500m (4min 51.61sec, 609).
It was Adams' third decathlon.
He won in 2004 and came second to international Peter Cox (Ariki) in 2005.
Peter Bromley (Ariki) won the men's masters title with 3151 points.
His best score was in the 1500m where his time of 4min 59.55sec earned him 562 points.
Michael Jolly (Hill City) won the boys aged 14 octathlon with 2698 points with a solid all-round performance that included personal best performances in the 100m (12.86sec, 492), long jump (5.19m, 419) and shot put (8.23m, 380)A feature of the non-championship events was the return of Blair Stewart (Taieri), a 31-year-old Otago sheep farmer who has been off the scene for four years.
He proved that the time he spent away from the sport working in Western Australia has not lessened his skills when he won the men's javelin with a throw of 53.80m.
Stewart is Otago's best javelin thrower of the past 25 years and has won 11 Otago senior men's titles.
He also won a New Zealand junior title and won bronze and silver medals at the national senior championships.
His best distance is 68m.
He does not have any great hopes about his return to the sport.
"I just came back to say hello to everyone," he said.
Stewart inspired Kane Russell (Hill City) to produce his best form when he won the aged 15 and 16 javelin with 47.44m.
Hill City's Toby Flett (16) leads the 100m national rankings in his age group and was hoping for a legal time to clinch his place in the New Zealand team for the Australian Youth Olympics in Sydney in January. The team will be announced next week.
He looked on target when he followed Todd Mansfield (Taieri) home in his first race in 11.15sec.
Mansfield clocked 10.83sec.
But it could not be counted for national selection because the wind gauge was not working.
A rerun was held later in the meeting to give Flett a chance to reach his target, and he finished closer to Mansfield, who won the race in 11.02sec.
Flett clocked 11.10sec, but the wind reading was narrowly over the legal limit at 2.8m per second.
Flett also impressed in the 200m when he finished third behind the senior sprinters in 22.64sec.
Mansfield took charge down the straight to roar past Cory Innes (Taieri), who had held the advantage around the bend.
Mansfield was timed at 21.57sec and Innes at 21.79sec.
Biddy Skerten (Taieri), another member of the Merrilees stable, won the girls aged 15 and 16 400m hurdles in 66.18sec.
