This systematic review identified 14 trials (6 randomized controlled trials, 7 controlled clinical trials) that compared the clinical outcomes of operative and non-operative treatment of clavicle fractures in adults. The majority of identified trials focused on the treatment of middle-third clavicle fractures, with one controlled clinical trial assessing treatment outcomes in lateral clavicle fractures. The results from this systematic review indicated that there was moderate evidence (GRADE B) demonstrating operative treatment produced better functional outcomes and less disability at short-term follow-up, had a less common occurrence of delayed union and non-union, and had a similar risk of mild complication as non-operative treatment.