Patellar tendon rupture is a rarely reported injury in both veterinary and human medicine. In dogs, it is generally the result of a direct trauma, and predisposing factors similar to those in the human literature have not been identified. A seven-year-old sexually intact male Poodle weighing 4.4 kg was admitted to the Veterinary Medical Teaching Hospital with a history of acute onset hindlimb carrying-leg lameness after having a fallen on the day before. Physical examination confirmed a carrying-leg lameness of the right pelvic limb, with a pain response elicited during hyperflexion and extension of the stifle joint. Radiographs revealed abnormal proximal displacement of the right patella without any evidence of degenerative joint disease. Based on clinical presentation, physical examination and radiographic findings, right patellar tendon rupture was diagnosed and surgical repair was proposed. Arthrotomy was performed by incising the joint capsule laterally and parallel to the patellar tendon. Patellar tendon was ruptured nearby to the distal pole of the patella. Both ends of the patellar tendon were approximated by extension of the knee and sutured with nylon 3-0 in an interrupted suture pattern. In addition, the lateral and medial edges of the patellar tendon were approximated in the same way. Good apposition of the tendon ends was achieved intraoperatively. The Prolene 1.0 was placed through a hole drilled in the tibial tuberosity, distally, and encircled the patella proximally. Routine closure was performed. The patient was discharged with light bandage and an additional two weeks of activity restriction. The dog began to ambulate and bear weight on the operated limb within the first postoperative week. Progressive improvement occurred after this period, and it was re-examined 40 days later. At this time, the radiographs showed mild degenerative joint changes and the patella in its normal place. Early mobilization may also have had a positive effect on the range of motion and the hypertrophy of the periarticular soft tissues; it is also the current trend in human surgery in cases of tendon rupture and has been associated with a decrease in complications, such as adhesion formation, cartilage damage, and reduced range of motion. One year and eight months post-operatively, the dog had regained full activity and the gait was normal.