Both became the first sides to successfully defend World Cup sevens titles after their twin successes in Moscow four years ago.
The men's team had been in danger of being knocked out early in the tournament when they had three players sinbinned in their quarter-final against France, but still held on to win 12-7.
They then beat the heavily favoured Olympic champions Fiji 22-17 earlier on Sunday.
Molia's two early tries gave the All Blacks the momentum they needed against an England side who had upset South Africa 29-7 to set up the final at AT&T Park.
Michael Ellery narrowed the gap to 14-7 at halftime, but Joe Ravouvou extended the lead before England's Ruadrih McConnochie crossed to put pressure on the New Zealanders.
New Zealand replacements Akuila Rokolisoa and Trael Joass, however, finished off the scoring to make the side the first to win three sevens World Cup titles. They also won in 2001.
"It's massive," captain Tim Mikkelson said. "We knew it would be tough. We were tested out there.
"Against France we were lucky not to get knocked out, we rose against Fiji and then beat a very good England side, who we thought we were the form team heading into it."
South Africa's men finished third, beating Fiji 24-19, while Olympic champions Australia beat the United States 24-14 on Saturday to clinch third in the women's tournament.
(Reporting by Greg Stutchbury; Editing by Ian Ransom)
