City confirmed on Saturday morning the 18-year-old has signed until the end of the season. The teenager becomes City's second deal of the January window after the permanent addition of Canadian international winger Ali Ahmed from MLS side Vancouver Whitecaps.
As first reported by this newspaper, City are believed to have beaten off a number of Championship clubs to land Amass, with the likes of Stoke and Watford also linked to the Manchester United youngster this month.
“I've spoken with Ben (Knapper) and the gaffer. They've both told me that they've been watching me since Sheffield Wednesday and a bit before that, and they've liked what they've seen,” said Amass, who will wear the number two shirt.
"They like the way that I carry the ball, the way that I am on the ball, the hard work that I show. They spoke to me and said they see that I can do good things here, they believe that it'll be a benefit for the club and for me, so it should be good both ways."
City sporting director Knapper, speaking to the club’s official site, added: "We're delighted to welcome Harry to the football club.
"Whilst still in the very early stages of his journey in the professional game, his talent was evident for all to see during the first half of the season throughout an impressive loan spell at Sheffield Wednesday.
"He has shown he is clearly ready to compete, and excel, at this level, and he'll add quality and strengthen the left-back position for us.
"He's fit and ready to go, and we're looking forward to him helping the group and contributing to moving the club up the table for the remainder of the season."
Amass arrives at Carrow Road having spent the first half of the campaign on loan at stricken Sheffield Wednesday, impressing for the strugglers before the terms of his initial loan agreement ran out earlier this month.
City have moved to sign a left back after Lucien Mahovo suffered a muscular injury in training that is expected to leave him sidelined for a prolonged period. Jeffery Schlupp remains sidelined with a hamstring injury, leaving Ben Chrisene as their only fit senior option in that area.
Amass, 18, began his career at Watford before signing for Manchester United in 2023. He made a match day squad for the first time seven months later in a 2-2 draw with Jurgen Klopp’s Liverpool, but didn’t get off the bench.
His senior debut for United came as a substitute in their 3-0 victory over Leicester in the Premier League in April 2025. He went onto made four starts that season under Ruben Amorim before joining Sheffield Wednesday on loan last summer.
Amass made 22 appearances for the Owls before departing earlier this month after his loan deal at Hillsborough expired.