Grigor Dimitrov also will be playing in his first W&S final after outlasting John Isner 7-6 (4), 7-6 (10) in the first men’s semifinal.
Muguraza, the Wimbledon champion, will meet the winner of the later semifinal between Simona Halep and Sloane Stephens.
The final Sunday will be the first on American soil for Muguruza, who lost to Pliskova in last year’s W&S semifinals. The Spaniard had lost six straight matches against Pliskova since winning their first in 2013.
“I was very precise with my shots,” Muguruza said. “I wanted to be more aggressive and take my shots. I felt pretty good out there — under control. Everything went my way.”
Muguruza won when the top-ranked Pliskova sailed a forehand long on the fifth match point. Pliskova, who played part of one match and all of another Friday after rain forced postponements Thursday, had 28 unforced errors to Muguruza’s 13.
Muguruza was coming off playing the tournament’s longest match, a 2-hour, 45-minute three-set win over Svetlana Kuznetsova on Friday. That followed a 2-hour, 18-minute win over Madison Keys on Thursday, when she fought off three match points.
“I don’t think I played my best tennis today,” Pliskova said. “I think the energy was pretty low from my side. Obviously, a tough schedule for me the last two days — three matches in about not even 24 hours.
“I think she played very solid, not missing much and obviously serving well. Everything started, I think, in the first game of the first set.”
Muguruza took charge early, breaking Pliskova in the first and last games of the first set.
She gained a second-set edge with a backhand winner on break point for a 4-2 lead before closing it out in 1 hour, 19 minutes.
The 11th-ranked Dimitrov, who lost in the last year’s semifinal to eventual champion Marin Cilic, had just one double fault and finished with nine unforced errors to No. 19 Isner’s 28 in the 2-hour, 3-minute match. The Bulgarian will play the winner of the semifinal between Nick Kyrgios, who knocked out second-ranked Rafael Nadal in straight sets in a Friday quarterfinal, and David Ferrer.