We sought to determine what effect the size of a displaced coronoid fracture fragment in Monteggia injuries has on clinical outcome. Sixty-seven patients presented to an academic medical center for operative fixation of a Monteggia fracture. Radiographs were assessed for length and height of the displaced coronoid fragment using measuring tools in our center's imaging archive system. Data were analyzed using binary logistic or linear regression, as appropriate, controlling for sex, age, and Charlson Comorbidity Index. Outcome measurements included radiographic healing, range of motion, postoperative complications, and reoperation. The cohort had a mean follow-up of 16.7 months. Mean coronoid fragment area was 362.4±155.9 mm2. Elbow range of motion decreased by 3.8° of elbow flexion (P<.001), 3.3° of elbow extension (P<.001), and 3.8° of forearm supination (P=.007) for every 1-cm2 increase in coronoid fragment area. Complications (P=.012) and reoperation (P=.036) were associated with increasing coronoid fragment area. Nonunion rate, nerve injury, and pronation range of motion were not correlated to increasing coronoid fracture fragment area (P=.777, P=.123, and P=.351, respectively). As displaced coronoid fragment size increases in Monteggia fracture patterns, elbow range of motion decreases linearly. Coronoid displacement was also associated with increased rates of postoperative complication and need for reoperation. [Orthopedics. 2024;47(1):15-21.].