The 22-year-old trained with his new team-mates on Friday after arriving from Anfield.
Ward is the first goalkeeping change since the departure of coach Jim Leighton and appointment of Gordon Marshall, and the loanee will compete with Scott Brown and Jamie Langfield for the number one jersey.
The signing will raise question marks over Reppublic of Ireland Under-21 squad member Danny Rogers' long-term future at Pittodrie.