Objective: To observe the clinical efficacy of minimally invasive treatment for comminuted fractures of long bones using adjustable carbon fiber three-dimensional external fixator-assisted closed reduction and internal fixation, providing practical evidence for clinical treatment. Methods: Ninety patients with comminuted fractures of long bones admitted to the orthopedics department of our hospital from January 2024 to January 2026 were selected as the study subjects. They were randomly divided into an observation group and a control group using a random number table method, each with 45 patients. The control group underwent traditional open reduction and internal fixation, while the observation group underwent minimally invasive treatment using adjustable carbon fiber three-dimensional external fixator-assisted closed reduction and internal fixation. Surgical-related indicators (operative time, intraoperative blood loss, hospital stay), fracture healing status (fracture healing time, excellent and good rate of fracture healing), postoperative complications, and limb function recovery before and after treatment were compared between the two groups. Results: The observation group had significantly lower operative time, intraoperative blood loss, hospital stay, healing time, and complication rate compared to the control group (all P < 0.05). The excellent and good rate of fracture healing in the observation group was significantly higher than that in the control group (P = 0.013 < 0.05). At 3 and 6 months after treatment, the Johner-Wruhs scores of both groups were significantly higher than those before treatment, and the scores in the observation group were significantly higher than those in the control group (all P < 0.001). Conclusion: Minimally invasive treatment for comminuted fractures of long bones using adjustable carbon fiber three-dimensional external fixator-assisted closed reduction and internal fixation offers advantages such as minimal surgical trauma, less intraoperative bleeding, rapid postoperative recovery, good fracture healing, and fewer complications. It effectively promotes limb function recovery in patients, demonstrating definite clinical efficacy and warranting widespread application.