Kristoffer Ajer has completed a medical ahead of a move from to Brentford.
The Bees will pay a fee in the region of £13.5m for the 23-year-old Norway centre-back.
Ajer was left out of Celtic’s pre-season game last weekend and is not expected to feature against Brentford’s sister club FC Midtjylland in a Champions League qualifier tonight.
Brentford have made signing a new centre-back one of their priorities this summer.
Meanwhile, they have confirmed the signing of Nigerian midfielder Frank Onyeka and are set to snap up Chelsea’s teenage midfielder Myles Peart-Harris.