Background: This study evaluates whether a circumferential cast compared to a plaster splint leads to less fracture redisplacement in reduced extra-articular distal radius fractures (DRFs). Methods: This retrospective multicentre study was performed in four hospitals (two teaching hospitals and two academic hospitals). Adult patients with a displaced extra-articular DRF, treated with closed reduction, were included. Patients were included from a 5-year period (January 2012–January 2017). According to the hospital protocol, fractures were immobilized with a below elbow circumferential cast (CC) or a plaster splint (PS). The primary outcome concerned the difference in the occurrence of fracture redisplacement at one-week follow-up. Results: A total of 500 patients were included in this study (PS n = 184, CC n = 316). At one-week follow-up, fracture redisplacement occurred in 52 patients (17%) treated with a CC compared to 53 patients (29%) treated with a PS. This difference was statistically significant (p = 0.001). Conclusion: This study suggests that treatment of reduced DRFs with a circumferential cast might cause less fracture redisplacement at 1-week follow-up compared to treatment with a plaster splint. Level of Evidence Level III, Retrospective study.