The London, Ont., native skated under 38 seconds in both runs. Her times of 37.997 and 37.884 brought her in at 75.88. Calgary's Anastasia Bucsis took the silver in 76.70 and Danielle Wotherspoon of Red Deer, Alta., captured the bronze in 77.57.
The men's 500-metre race was won by Edmonton's Jamie Gregg with a combined time of 69.50 seconds (34.69, 34.81). Montreal's Muncef Ouardi was second in 69.82 and Lacroix-Boisvert of Sherbrooke, Que., third in 70.09.
Nesbitt also won the women's 1,000, 1,500 and 3,000-metre races in Calgary this week.
"(The 500s) were good races," said Nesbitt, the gold-medal winner in the 1,000 metres at the 2010 Olympics.
"Those are the two fastest times for me this year and only the third and fourth times I've skated under 38 seconds. I'm happy with that.
"I feel there is still room for improvement. The second race I had one of my fastest starts ever but I had trouble setting up the second corner. I didn't set it up properly. I was a bit unstable, so I know I can go faster than that."
Nesbitt previously had a 38.31 when she placed fifth at a World Cup in Heerenveen, Netherlands, in early December.
The world 500 metre record is owned by Jenny Wolf of Germany, who skated 37.00 in Salt Lake City, Utah, in 2009. Wolf also has the two-race 500-metre mark of 74.42 seconds, which she recorded in Calgary in 2007.
Nesbitt will now go for her fourth straight 1,000-metre win this season on the World Cup circuit Jan. 21-22 in Salt Lake City. She holds the World Cup lead at both that distance and 1,500 metres heading into that World Cup, having also picked up two wins and a silver in the 1,500 in Europe before Christmas.
After Salt Lake City the focus shifts back to Calgary for the world sprint championships Jan. 28-29.
Gregg will be there too. He secured his spot at the worlds by winning both the 500-metre and 1,000-metre Canadian titles.
"I'm happy with my two races (Sunday)," Gregg said.
"I still need to work on my start positions. I was a little bit off both races; slipped a bit and lost some time there. I will work on my corners, my entries. Everything can be a little bit sharper and the tenths (of a second) will come down with that."
Gregg has competed in only one other major international event in Calgary — a World Cup — so he is looking forward to skate there.
"Being at home is going to be incredible," he said. "The World Cup was incredible and the world championships is going to be even more exciting."
Speed Skating Canada officials said they will announce who will join Nesbitt and Gregg on the host's team for the world sprint championships later this week. Calgary's Denny Morrison, who has a World Cup bronze in the 1,000 this season, tweeted Sunday night that he had qualified.
Winnipeg's Tyler Derraugh won Sunday's 20-lap mass start men's race in 10 minutes 32.33 seconds. Philippe Riopel of Repentigny, Que., won the silver (10:33.15) and Leo Landry of Chelsea, Que., took the bronze (10:33.45). The women's 15-lap mass start gold went to Tori Spence of Kamloops, B.C., in 8:57.07. Lauren McGuire of Ottawa took second (8:57.51) and Ashley Nelson of Nelson B.C., third (8:57.07).