MacLeod (30) was the first competitor from Australia and New Zealand to finish on the 2.2km Canberra course, the venue for next year's world championships.
She was timed at 3min 24.85sec, 8sec ahead of Queenstown's Scarlett Hagen, who finished 11th.
"I'm over the moon," MacLeod said on her return to Dunedin yesterday. "My result was so much better than I expected."
It was her first World Cup event since finishing 13th at Colorado in 2001.
"It was a pleasant surprise and an awesome day for me," MacLeod said. "It has inspired me to aim for a higher place at next year's world championships."
The event was dominated by European riders, with Tracy Moseley (Britain) finishing first in 3min 10.43sec from world champion Rachel Atherton (Britain), 3min 14.51sec, and Sabrina Jonnier (France), 3min 14..66sec.
There was constant rain and the course became muddy. MacLeod used her experience to ensure she made no mistakes.
She almost came to grief when she crashed on a jump in the qualifying round when she finished 18th. Just 20 riders qualify for the final round.
MacLeod spent five weeks training and racing at the Whistler skifield in North America and finished second in the Giant Slalom to Anneke Beerten (Netherlands) at the annual Crankworx free ride festival.
"I competed in both cross-country and downhill events at Whistler and was a lot fitter," MacLeod said.
"I worked a lot on the jumps and really got into the groove. It helped me at Canberra because there were a lot of big jumps on the course."
MacLeod came back into serious mountain biking in time for the world championships in 2006, and last February regained the New Zealand downhill title that she last won in 2001.
MacLeod (30), a qualifications assessor for Work and Income in Dunedin, was one of New Zealand's most promising downhill riders when she broke her elbow at Vermont in 2001. It meant missing the 2001 world championships in Colorado after being named in the New Zealand team.
She became disillusioned and gave up the sport.
"My heart was not in it any more," she said.
"I was not enjoying biking and had lost the desire to race."
But MacLeod still had the ambition to represent New Zealand at a world championships and saw her chance when the event was allocated to Rotorua. She finished 16th at the 2006 world championships.
A torn cartilage in her left knee put MacLeod out of the 2007 national series and she was only able to resume racing last season after an operation 17 months ago.
• Former Dunedin rider and Olympian Kashi Leuchs finished 16th in the 38km men's cross-country and was the best-performed New Zealand rider.
