[Objective] To compare the clinical efficacy of two approaches for open reduction and internal fixation (ORIF) of trimalleolar fractures. [Methods] From December 2014 to December 2020, 32 patients received ORIF of trimalleolar fractures, including 17 patients with posterior malleolus exposed by posterolateral approach (lateral group) and 15 patients with posterior malleolus exposed by posteromedi- al approach (medial group). The perioperative and follow-up documents were compared between the two groups. [Results] Anatomic reduc- tion was achieved in all patients of both groups, without complications such as nerve and blood vessel injury. There were no significant differ- ences in operation time, intraoperative blood loss and wound healing between the two groups (P＞0.05). The incision length for exposing poste- rior malleolus was significantly longer in the lateral group than in the medial group (P＜0.05). All patients in both groups were followed up for more than 1 year, without a significant differences in the time to resume full- weight activity, as well as AOFAS score and ankle ROM be- tween the two groups at latest follow-up (P＞0.05). [Conclusion] Both approaches can expose the posterior malleolus effectively in open re- duction and internal fixation of trimalleolar fractures, which should be selected based on the concrete condition of the posterior malleolus fractures.