Pascoe finished nearly a full second ahead of Bianka Pap of Hungary and Alice Tai of Great Britain.
She went into the final having qualified fastest in the heats.
Pascoe regained the title she lost in London four years ago, but says she found the final pretty tough.
"I went out in the first 50 metres pretty much towards race plan and then the last 50 metres was hard and they came back in the last 25 [metres]," she said.
"It was just about guts and digging deep. Tonight was about coming out and getting the gold medal and that is exactly what I have done.
