Background: The probability of returning to competition for injured baseball pitchers is similar after ulnar collateral ligament (UCL) repair as after UCL reconstruction, but the time to return is significantly quicker after UCL repair. Previous research has found no differences in pitching biomechanics between pitchers with and without a history of UCL reconstruction, but pitching biomechanics after UCL repair has not been studied. Hypothesis: There will be significant differences in pitching biomechanics between pitchers returning to play after UCL repair and pitchers with no injury history. Study Design: Controlled laboratory study. Methods: A total of 33 pitchers were tested shortly after UCL repair (9.8 ± 2.6 months) and compared with a matched group of 33 uninjured pitchers. Each group comprised 14 college pitchers and 19 high school pitchers. Shoulder and elbow passive ranges of motion were measured. The biomechanics of 10 fastballs was then collected using a 12-camera automated motion capture system. Ball velocity was measured using a separate 3-camera optical tracking system. Data were compared between the UCL repair group and the control group using the Student t test (significance set at P <.05). Results: There were no differences in passive range of motion or fastball velocity between the 2 groups. There were no differences in joint kinetics during pitching, but 3 kinematic variables showed significant differences. Specifically, the UCL repair group produced less elbow extension (flexion: 27° ± 6° vs 24° ± 4°, respectively; P =.03), less elbow extension velocity (2442 ± 367 vs 2631 ± 292 deg/s, respectively; P =.02), and less shoulder internal rotation velocity (6273 ± 1093 vs 6771 ± 914 deg/s, respectively; P =.049) compared with the control group. Conclusion: Elbow extension, elbow velocity, and shoulder velocity differed between pitchers with a recent history of UCL repair and a matched control group, but it is unclear whether this has clinical significance, as there were no differences in ball velocity and passive range of motion. Furthermore, it is unknown whether these few differences in pitching biomechanics resolve with time. Clinical Relevance: Elbow and shoulder kinematics during pitching might not be completely regained within the first year after UCL repair, although passive range of motion and pitch velocity show no difference in comparison to other healthy pitchers.