Pickens started on pole after advancing forward in the qualifying heats and saw off a fierce challenge by American Rico Abreu in the early stages of the race, before Abreu dropped a cylinder in his engine.
The next group of Americans to make it difficult for the Kiwi was Christopher Bell, Darren Hagen and Bryan Clauson.
But with 12 laps remaining all three US drivers were involved in a tangle, that also took out hard-charging Mosen, who had passed 18 cars and was showing promise.
In the end, though, it was Pickens who took the chequered flag, followed by a restarted Clauson and Brock Mascovich.
"Those Americans had their noses in front a few times but I was getting out wide on those restarts which seemed to be helping," said Pickens.
"Those guys are the best in the world so it's special to beat them."
The midgets will be taking a short break from the New Zealand scene as they head to Australia for three rounds of the Midget World Series.
Meanwhile, Pickens will soon return to the sprintcar division, where he has plied his trade with limited success this season.
"I've been out of the sprintcar for a while now, but we have the New Zealand championships coming up and we should be okay once I get a bit of seat time," he said.
The next meeting at Western Springs is the Barry Butterworth Classic on February 22, in which the fastest cars will come from the rear of the grid in all classes.