Objectives: To examine the efficacy and clinical and radiological outcomes of the use of a streamlined clavicle plate® (MEIRA, Aichi, Japan) for midshaft clavicular fractures.Methods: This was a retrospective cohort study of 155 patients with displaced midshaft clavicular fractures treated using a streamlined clavicle plate between 2015 and 2019 in 18 hospitals across Japan. A questionnaire regarding bone union and postoperative complications was used, and 136 cases were followed up for one year or until bone union. Plate fitting was evaluated retrospectively using surgical records, radiographic findings, and surgeon’s opinion.Results: During surgery, plate bending was needed in 19 cases (12.3%), poor fitting was observed in 8 cases (5.2%), and bone union was achieved in 133 cases (97.8%). Total implantation failure, including plate breakage and screw loosening, occurred in 10 cases (6.5%) from the intraoperative to postoperative period. Subjective complications were observed in 26 cases (16.8%): incongruity around the surgical scar or in the anterior chest in 23, and contracture of the shoulder in three. Plate removal was performed in 66 cases (48.5%) per patient’s request.Conclusion: The use of a streamlined clavicle plate is effective for midshaft fractures of the clavicle, and the success rates of bone union and implantation using this approach are comparable to those of other existing plates.