Objective: Diagnosing rib fracture with radiography is sometimes very difficult. Accurate disclosure of rib fracture can contribute to more specific medication and other alternative managements. Case report: A female patient with the history of breast cancer bothered by persistent chest wall pain with negative finding of rib radiography, but subsequently diagnosed with rib fracture by high-resolution sonography. Her pain intensity was significantly reduced after ultrasound-guided fracture site injection of local anesthetics. Conclusion: High-resolution sonography is more sensitive in detecting rib fracture and it also possesses the capability of distinguishing between metastatic lesion and simple fracture.