The Luton schemer, 27, has become the Tigers’ first summer addition after agreeing a two-year deal, with the club holding the option of a further year.
Moncur has previously worked alongside McCann during a loan spell at Peterborough in the first half of the 2016-17 season.
McCann said: “We’re delighted to have brought George to the club. There was a lot of competition for his signature and I worked with him for a brief period at Peterborough.
“George is a bubbly character and his nature and attitude will fit into our group and he will complement the attacking players in our team.
“He’s very attack-minded and travels with the ball at speed. He can play in any of the front three positions or as a 10, and loves to take the ball off his back foot and get at people.
“He knows what it takes to win having achieved promotions in his career and he was part of a successful Luton team last year in the Championship.”
New Doncaster Rovers signing Ben Close admits that the time was ripe for a new challenge in his career after turning down a new deal at boyhood club Portsmouth to head north.
The 24-year-old midfielder, who has penned a three-year contract, has become the first arrival of the Richie Wellens era.
With his deal at Pompey expiring at the end of June, Close had been offered fresh terms for the next two seasons by the south coast club, who were not in a position to take up an option of an extra season on his existing contract – which would have increased the player’s salary.
But the desire to start a new chapter in his career was paramount in his decision.
He said: “I was offered the new deal, but I just got to the stage in my career where a new challenge felt imminent for me. It felt like the natural next step in my career.
“I always felt that leaving Pompey would be a bit of a shock but it felt natural and the next thing to do in my career.
“To be the first signing (of the Wellens era) is great for me and to be joining a club like Doncaster Rovers is a massive challenge for me and a really exciting one.
“To have the manager show his interest and how much he wanted me was a big pulling factor and I can’t wait to get going for him.”
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