The Cubs didn't officially announce the move until the afternoon, but Montero confirmed it to MLB.com and took to social media to thank the city of Chicago and teammates for their support.
Montero's comments following Tuesday night's 6-1 setback to the Nationals likely played a role in the Cubs' decision to let him go.
"That's the reason they were running left and right (Tuesday) because they were slow to the plate," Montero said of his pitchers, including Arrieta, following the loss. "Simple as that. It's a shame it's my fault because I didn't throw anyone out.
"It really (stunk) because the stolen bases go on me, but when you really look at it the pitcher doesn't give me any time, so yeah, 'Miggy can't throw anyone out,' but my pitchers don't hold anyone on."
Montero, who was 1-for-32 in throwing out basestealers this season, told ESPN 1000 Chicago on Wednesday that he apologized to Arrieta for his comments.
"I called Jake to apologize," the 33-year-old Montero said. "It was the heat of the moment. He's grinding out there, I'm grinding behind the plate. It's tough. It's the heat of the moment. I said what I said -- yes, I'm responsible. I talked to him to apologize because I feel like I should step up and apologize and I did.
"... Jake was totally fine (with the apology) He actually agreed with me. We're cool. He was totally cool."
Arrieta admitted that his delivery could've been faster.
"I didn't do him any favors -- slow to the plate," Arrieta said before Wednesday's game in Washington.
Teammate Anthony Rizzo wasn't cool with Montero's comments and vented his frustration to ESPN 1000 Chicago.
"We win as a team, we lose as a team," Rizzo said. "If you start pointing fingers that just labels you as a selfish player. I disagree. We have another catcher (Willson Contreras) who throws out everyone who steals, and he (catches for) Jon Lester who doesn't pick over. It's no secret. Going to the media with things like that, I don't think it's very professional."
Montero batted .242 during his three seasons with the Cubs. He was demoted to backup last year with the arrival of Contreras, and had started 28 games this year while Contreras started 49.
The Cubs called up catcher Victor Caratini from Triple-A Iowa.
Caratini, 23, is batting .343 with eight home runs and 54 RBIs in 68 games with Iowa.