The 23-year-old central midfielder, who was unveiled as a Sulphurites player on Wednesday, spent last season playing in the Championship with Wycombe Wanderers.
And the Chairboys were keen to keep hold of the former Middlesbrough trainee as they prepare for life back in League One following their demotion from the second tier, but lost out to the Town boss in the battle for his services.
“I think it is a bit of a coup for us and I’d say it’s very positive for the club that we’re able to attract a player of Alex’s quality, who was playing Championship football last season,” Weaver told the Harrogate Advertiser.
“I know that Wycombe wanted to keep him, but Alex was keen to come back up north for family reasons.
“He’s from County Durham and both him and his partner wanted to be a lot closer to home, so we were fortunate there. His situation and the timing of it has landed in our lap quite nicely.
“Once we made Alex an offer he met it with such enthusiasm that it became very apparent that he really wanted to come here, which I am delighted about.”
Darlington-born Pattison came through Middlesbrough's academy and got his first taste of senior football in December 2017 during the first of two loan spells with York City.
He then made the temporary switch to Yeovil Town for 2018/19, joining Wycombe on a permanent deal following his release by Boro at the end of that campaign.
He helped the Chairboys achieve promotion into the Championship during his first season at the club, featuring 24 times in all competitions for Gareth Ainsworth’s side to trigger a one-year contract extension.
He was something of a bit-part player in the second tier last term, making just four Championship starts and two substitute appearances as Wycombe were relegated straight back to League One.
Pattison will wear the number 16 shirt at Harrogate, recently vacated by veteran striker Jon Stead, who has retired from the game.