Mason, who turns 20 today, won the four-day event with a final score of 15.43 points from Ella Williams (Whangamata) 14.9, Jessica Santorik (Raglan) 12.7 and Hayley Coakes (Dunedin) 8.
She won her first title at Piha in 2004, as a 13-year-old, and spent the past six years living on the Gold Coast with her family before returning to Gisborne a month ago.
She honed her skills on the Gold Coast and won the Australian junior series shortly before returning to New Zealand.
Mason was fourth in the world junior championships in 2006 and 2008 and was also the Australasian junior champion.
This was her first competition in New Zealand for seven years.
"I'm happy. It's the most prestigious title in New Zealand women's surfing," she said. "It's cool to win it again."
Mason was surprised when she won the title in 2004.
"It was a bit of a shock," she said. "It was a last-minute decision to enter the women's open event. I was overwhelmed.
"But the win today means just as much. It was good to come back home and win it again."
The tricky conditions yesterday made it difficult to find suitable waves that linked up. But it did not upset Mason.
"I am used to conditions like this in Australia," she said.
She was trailing 15-year-old Ella Williams (Whangamata) until she caught the winning wave in the last few minutes.
"I saw a little wedge peak come through," Mason said. "It looked a good one and nobody else was around, so I thought I'd give it a go ..." That wave was worth 8.6 points, enough to give her a win over Williams by half-a-point.
Williams, a pupil at Whangamata Area School, has been surfing since the age of 4 and felt at home in the conditions.
This was the first time she had made the open women's final.
"It's my best-ever result and I'm stoked with it," she said. "It felt cool to finish so close. I'm happy with what I did."
Her best wave scored 8.17 points.
"I had a good start and a good finish," Williams said. "I had a few cutbacks and a floater to finish."
Williams has a clear goal, "to become the best surfer in the world".
It was the first time Coakes (27), a Dunedin machinist, had reached the final at a New Zealand championships.
