Importance: Complications affect treatment outcomes and quality of life in addition to increasing treatment costs. Objectives: To evaluate complication rates after the treatment of a distal radius fracture, to determine whether the rate or complication type is associated with treatment method, and to determine predictors of complications. Design, Setting, and Participants: The multicenter Wrist and Radius Injury Surgical Trial (WRIST), a randomized clinical trial, enrolled participants from April 10, 2012, to December 31, 2016. The study included 304 adults 60 years or older with isolated unstable distal radius fractures; 187 were randomized and 117 opted for casting. The study was conducted at 24 health systems in the United States, Canada, and Singapore. Data for this secondary analysis were collected from April 24, 2012, to February 28, 2018. Interventions: Participants opting for surgery were randomized to receive the volar locking plate system (n = 65), percutaneous pinning (n = 58), or bridging external fixation with or without supplemental pinning (n = 64). Patients who chose not to have surgery (n = 117) were not randomized and were enrolled for casting. Main Outcomes and Measures: Complication rate. Results: The WRIST enrolled a total of 304 participants, of whom 8 casting group participants were later found to be ineligible and were excluded from the analysis, leaving 296 participants. Randomized participants' mean (SD) age was 68 (7.2) years, 163 (87%) were female, and 165 (88%) were white. Casting participants' mean (SD) age was 75.6 (9.6) years, 93 (84%) were female, and 85 (85%) were white. The most common type of complications varied by treatment. Twelve of 65 participants (18.5%) in the internal fixation group reported a median nerve compression, while 16 of 26 participants (25.8%) who received external fixation and 13 of 56 participants (23.2%) who received pinning sustained pin site infections. Compared with the internal fixation group, complication rate for any severity complication was higher in participants who initially received casting (adjusted rate ratio, 1.88; 95% CI, 1.22-2.88), whereas the rate for moderate complications was higher in the external fixation group (adjusted rate ratio, 2.52; 95% CI, 1.25-5.09). Conclusions and Relevance: The distal radius fracture treatment decision-making process for older patients should incorporate a complication profile for each treatment type. For example, external fixation and pinning could be used for patients after apprising them of pin site infection risk. Internal fixation can be done in patients with high functional demands who are willing to receive surgery. Internal fixation use should be substantiated owing to the time and cost involved. Trial Registration: ClinicalTrials.gov Identifier: NCT01589692.