Objective This study evaluated the diagnostic value of adding magnetic resonance imaging (MRI) to multimodal ultrasound for breast cancer, where multimodal ultrasound consisted of two-dimensional imaging and the strain ratio (SR) from elastography. Methods We enrolled 180 patients with breast lesions who were admitted to our hospital between August 2023 and August 2025. All patients underwent multimodal ultrasound and MRI examinations. Multimodal ultrasound included two-dimensional imaging and ultrasound elastography with strain ratio measurement. Breast cancer detection rates were assessed for each imaging method. The diagnostic performance of multimodal ultrasound alone, MRI alone, and the two methods combined was compared. Results Among the 180 patients, 82 (45.56%) had benign lesions and 98 (54.44%) had malignant lesions. The numbers of cases consistent with pathological diagnosis were 152 for multimodal ultrasound, 145 for MRI, and 160 for their combination. The sensitivity of the combined diagnosis was 95.92%, which exceeded that of multimodal ultrasound alone (84.69%) and MRI alone (79.59%). The negative predictive value of the combined diagnosis was 94.29%, which was significantly higher than that of MRI alone (77.01%, P<0.05). Conclusion Combining MRI with multimodal ultrasound based on SR and two-dimensional ultrasound significantly improves the differential diagnosis of breast cancer. This strategy compensates for the limitations of using a single modality and provides a more reliable imaging basis for clinical diagnosis and treatment decisions.