Despite an 0-for-4 performance at the plate, the 21-year-old did reach base and score, and afterward called the whole day "amazing."
"It means a lot for me," said Montero, who was the designated hitter and batted seventh. "Thank God I'm here for the first time -- first opportunity that I had to play in the big leagues. It was amazing for me today."
Ranked as the No. 6 prospect in all of baseball by MLB.com, Montero's first at-bat came with some pressure, and he didn't shy away from admitting the natural reaction: he was nervous.
With the Yanks already ahead 1-0 in the bottom of the first against Boston's Jon Lester, Montero went down swinging with the bases loaded. The pitch was a 2-2 cutter, breaking low and inside.
"Yeah, I was [nervous]. I was," Montero said. "First time, you know, I tried to put the ball in play. ... When I first stepped in the box, I'm just like, I'm trying to be calm and be relaxed, be relaxed at the plate and put the ball in play. That's it."
Montero, who bats right handed, hit .288 with 18 home runs and 67 RBIs in 109 games for Triple-A Scranton/Wilkes-Barre this season. The Yankees are especially hoping that his power numbers against left-handed pitchers will translate to the big league level, owning a 1.039 OPS in 119 at-bats this year.
"I thought it was pretty good," manager Joe Girardi said of Montero's approach. "He's never seen Lester. I thought he had some good swings on some balls. [He] ends up getting on and scoring the go-ahead run, but I thought his approach was good."
Montero flied out in the third and grounded out in the fifth before being hit by Alfredo Aceves in the seventh. After a pitching change, Montero scored the go-ahead run on Russell Martin's two-run double. Montero flied out again in his last at-bat in the ninth.
Girardi said that he isn't sure if he will start Montero behind the plate this year, but he would like to see him catch at some point. As for Friday at home against the Blue Jays, Montero would love to be in there any way he can be.
"I'm looking forward. I hope I'm playing tomorrow," he said. "I don't know what they're going to decide."
The Yankees were looking for Montero to step up and claim the backup catcher job this spring when Francisco Cervelli went down to injury, but Montero admittedly pressed and the team went with journeyman Gustavo Molina instead, sending Montero to Triple-A.
"I really believe that the young man put too much pressure on himself; rightfully so," Girardi said. "You're  years old, you want to be in the big leagues, and you've got an opportunity to make the team. Who wouldn't put pressure on themselves?"
Montero said that he learned a measure of patience from the experience.
"I have to be calm all the time, I have to slow down everything," Montero said. "It's the same baseball for me. I mean, I've got to be like that."
Should Montero hit as he has in the Minors, the Yankees will face the decision of whether they should carry him on the postseason roster -- something Girardi said they wouldn't rule out. And while Montero waited for his first big league at-bat, he's not afraid to at least fantasize about October.
"There can be a chance," Montero said. "I've got to do my best over here, talk to everybody, learn from everybody here on the team. I've got to do my best. That's it."
Montero said that his parents and girlfriend have tickets and made it to Boston to share the experiences of his first day.
"It's unbelievable," Montero said. "Being here is amazing. For my life, my family is so happy. I'm really happy to be here. It's the best."
Bryan Hoch is a reporter for MLB.com. Follow him on Twitter at @bryanhoch. Evan Drellich is a reporter for MLB.com. Follow him on Twitter @EvanDrellich. This story was not subject to the approval of Major League Baseball or its clubs.