The Accies man will move to Pittodrie when his deal expires at the end of the season, despite rumoured interest from Crystal Palace.
The 18-year-old came through the ranks at Hamilton and has made 14 appearances for the club since making his debut in January, the latest being in the 2-0 win over Ross County last week when he came off the bench to set up the second goal for David Templeton.
Speaking to the club website, Derek McInnes said: “Lewis is a promising young player who I look forward to working with and developing here at Pittodrie.”
After seeing his side lose to Dundee on Saturday afternoon, Accies boss Martin Canning admitted the club had no choice but to let him go despite offering him a new deal.
“The club has been speaking to him for the last couple of months about staying so it’s not caught us on the hop,” he said.
“We have a wage structure we work within and we have been speaking to Fergie and it’s not been able to get over the line.”