Verlander, 34, and Upton, 25, were engaged in May of 2016 and have been dating since 2014.
Upton posted a photo on her Instagram account on Oct. 23, showing herself with a group of four other women. She was sporting a "bride" hat during what appeared to be a bachelorette party at the Plaza Hotel in New York City.
The former Cy Young and MVP award winner joined the Astros on Sept. 1 after being traded from the Detroit Tigers. Verlander spent more than 12 seasons with the Tigers. He posted a 1.06 ERA in five appearances this season for the Astros.
Verlander posted a 2.21 ERA and a 4-1 record this postseason. He took a loss in Game 6 of the World Series after allowing two earned runs in six innings to the Los Angeles Dodgers.
Verlander wasn't the only Astros player hearing wedding bells Wednesday night. His teammate Carlos Correa popped the question to his girlfriend after the Game 7 victory. Verlander's old team sent him well wishes after he earned the title.
"For someone who has earned several honors over his career, we know this one is special. Congrats @JustinVerlander," the Tigers tweeted.