The German midfielder has endured a tough start to the Premier League season, with some reports suggesting he had fallen out with the new manager.
Ahead of the Gunners' win over West Ham United, reports emerged of a bust-up between Ozil and Emery in training, although the club confirmed the player was ill.
Monreal echoed the club's story and feels the World Cup winner is being treated unfairly.
"People have been a bit unfair with him," Monreal was quoted as saying by SkySports.
"He is a very famous player and obviously people love talking about him. Recently, it is always bad things. Like last time, he was sick and that's why he didn't play.
"People started to invent that he had a problem with the manager. It wasn't like that. He got a cold, he was sick, that's it. That's why he didn't play."