Montoya received the suspension at the NRL judiciary on Tuesday evening after referring to North Queensland winger Kyle Feldt as a "fa***t".
While Feldt lay on the ground awaiting treatment during the Warriors' 25-24 win on Friday, Montoya yelled: "Get up Kyle, you fa***t".
In a statement from the Warriors Montoya said he was "fully remorseful."
Montoya had pleaded guilty to a contrary conduct charge.
"I acknowledge and accept that the comment I made on Friday night is completely unacceptable," said Montoya.
"If you know the person I am you would know this is completely out of character. I am fully remorseful for my actions.
"In saying all of this I would like to apologise to Kyle Feldt, to the NRL and to the gay community, and anyone else that I have offended, as I know and respect the work that the NRL has done to ensure inclusiveness and diversity within the NRL community.
"Moving forward I can only assure you that I have learned from this lesson and this will never happen again."
Vodafone Warriors CEO Cameron George said the club accepted the penalty.
"We know how disappointed Marcelo is with himself. He's devastated and we really feel for him and what he has been going through," he said.
"As a club we don't condone such behaviour in any circumstances and nor does Marcelo. He will learn from this and will use it to move forward from this episode and be the best person he can be. We'll offer him all the support he needs."
Meanwhile NRL CEO Andrew Abdo has told NRL.com that homophobic slurs will not be tolerated in the game.
"Rugby league is a game for everyone, that's what I love most about our game. I'm proud that we bring people together," Abdo said.
"It doesn't matter where you are born, your gender or sexual orientation - rugby league is for everyone.
"That's why Indigenous Round, Women In League Round, Multicultural Round and participating in the Mardi Gras every year are so important to us. These events represent and celebrate who we are and what we stand for.
"The homophobic language used in Friday night's game between the Warriors and the Cowboys was unacceptable. It will not be tolerated.