Monk has signed a three-year contract, and Maddison is confident that his experience in the Premier League and Championship can pay dividends.
"I'm really pleased," said Maddo. "He's an up and coming manager who's done well everywhere he's been so far.
"Garry got that Premier League experience at Swansea, then went to Leeds and built them up last season. They just missed out of the play-offs but he did a really good job there.
"If you ask Leeds fans they're disappointed to see him go but it's our gain. He's young guy who wants to be successful and is coming to a football club who have just dropped out of the Premier League.
"Garry's been there and knows what the league is about. Going to Leeds will have been a difficult move for him but I think it's stood him in good stead.
"When you're in the Championship you've got to scrap for things and he's certainly had to do that at Leeds.
"He's done well there and as I said, he's ambitious. I'm hopeful that we have a good season and that he can deliver."
Steve Gibson spoke exclusively to Maddo on BBC Tees following Boro's final home game of last season, when he outlined his desire to make an immediate return to the Premier League.
And Maddo believes Monk already has a strong foundation to build on at Boro, with many of the squad still around that initially won promotion to the top flight a year ago.
"I'm sure the chairman will back Garry to bring in the players who will hopefully take us straight back up," he said.
"It is a challenge being the manager of Middlesbrough Football Club. But the one thing Garry has in his favour is that he has a chairman that will totally support him.
"He doesn't get involved much and will let him get on with things as we've seen in the past. I think Garry will be happy with that.
"Coming to Boro the facilities are fantastic. He knows what's at his disposal and he'll know that the majority of players in that squad have been in the Championship and got promotion.
"So the base and core of the squad is one that is good and can challenge next season.
"You need those game changers and extra special talent in your side to change those games and I'm certain that Garry will be looking at those kinds of players already."