Purpose To assess the technical feasibility of contrast-enhanced ultrasound (CEUS) in the monitoring of non-infected long bone nonunion healing. Methods Twenty-five patients (16 males; mean age: 40.4 ± 11.7) with long bone nonunion were treated using surgery and mesenchymal stem cells and platelet-rich plasma. They performed CEUS up to 15 days before, 7 days, 4 and 8 weeks after treatment. To categorize the angiogenesis around the fracture site, the microvascular blood flow from CEUS was classified into four categories, depending on the portion of the investigated area that was involved in the neovascularization process: grade 0 = 0%; grade 1 = 0–30%; grade 2 = 30–70%; grade 3 = 70–100%. Nonparametric Friedman and Wilcoxon statistics were used. Results Before treatment, neovascularization was graded as 0 in 15/25 patients, as 1 in 10/25. Vascularity significantly increased over time ( P  < 0.001), namely: 1 (25th–75th percentile = 1–2) at 7 days; 2 (1–2) at 4 weeks; 3 (0–2) at 8 weeks. All patients but one showed early progressive increase in neovascularization well identified with CEUS at the fracture site. Conclusion CEUS is a feasible method to monitor healing in patients with long bone nonunion.