The Motherwell centre-back will move to Pittodrie this summer when his contract expires at the Lanarkshire side. He becomes the second SPFL star after Celtic captain Scott Brown to agree to join Stephen Glass’ revolution in the north east.
The Aberdeen manager welcomed to the signing as he looks to mould the first-team squad in his own image after taking over from long-term boss Derek McInnes last month.
He told the club’s website: “We are delighted to be able to add someone of Declan’s quality to the first team.
“He is one of the country’s top centre backs and played a prominent role in Scotland’s qualification for the Euro’s this summer.
“Declan was highly sought after and we beat off stiff competition to get him here, but it’s really encouraging to see he believes Aberdeen is the correct place for the next stage of his career and we are eagerly looking forward to working with him when he arrives in the summer.”
Gallagher has been a Motherwell player for the last two seasons after signing a pre-contract deal in April 2019 following a successful spell with Livingston. The defender spent the best part of five years with the West Lothian club, though he was imprisoned for over a year after being found guilty of assault which took place during his time with Dundee.
His impressive form at Fir Park earned him a Scotland call-up in October 2019. He’s since made seven appearances for Steve Clarke’s side and could yet feature at this summer’s European Championships.