Peritendinous adhesions are serious complications after surgical repair of tendons and can lead to poor functional outcome. In the present study, the tensile strength of repaired tendons was measured biomechanically in two groups using a rabbit Achilles tendon model, and the effects of Adcon gel on peritendinous adhesions and tendon healing were examined by means of histological and mechanical analyses. In the treatment group, the Achilles tendon was transected, followed by a primary repair using a modified Kessler technique, and Adcon gel was injected between the tendon and skin of the right leg. The same operation was done for the control group, and 1 mL of normal saline solution was applied locally in a similar fashion. The experimental protocols were approved by the local animal ethics committee. Microscopic evidence of the formation of adhesions and of inflammation was less in the treatment group than in the control group. There was no significant difference in the tensile load necessary to rupture the repaired tendons between the two groups. Adcon gel reduced the peritendinous adhesions histologically without impairing tendon healing, as determined with mechanical analyses. The use of Adcon gel may provide a simple means of preventing of postoperative peritendinous adhesions, thereby offering a beneficial effect on tendon repair.