Ellington put Cleveland in front by scoring on a dunk with 56.4 seconds remaining, helping boost the Cavaliers to their fifth win in eight games.
Cleveland trailed by eight going into the final period, but produced a 36-point fourth quarter during which Kyrie Irving scored 11 of his 20 points. Irving also had 10 assists and seven rebounds and his steal set up Ellington's go-ahead slam.
Ellington and Tristan Thompson both had 16 points and Thompson added 12 rebounds.
Utah was led by 25 points off the bench from Gordon Hayward.