Purpose <p>Idiopathic granulomatous mastitis (IGM) is a granulomatous condition with non-specific manifestations and a challenging diagnosis. This study aims to describe the appearance of biopsy-proven IGM lesions utilizing shear wave elastography (SWE) Young’s modulus.</p> Methods <p>We performed a retrospective search for pretreatment ultrasounds of IGM referred to two tertiary breast clinics over five years. Patients with at least one pre-treatment ultrasound and pathologically-proven IGM entered the study. Ultrasound and SWE were performed and interpreted by a breast imaging fellowship-trained radiologist. The data were analyzed using SPSS software.</p> Results <p>Among 201 pretreatment ultrasound, non-mass lesions (76%) and intercommunicating channels (52%) were the most common findings. All the patients had BIRADS of 4. The BIRADS of 4a was the most common (75%). Among 138 SWE, dark blue was the most common color in the center and periphery, with 80% and 76%, respectively. The mean stiffness (kPa) of the center was significantly higher than that of the peripheral parts in IGM lesions (<i>P</i> &lt; 0.001). None of the IGM lesions were hard enough to prevent sound waves from effective propagation.</p> Conclusion <p>Although IGM mostly presents in non-specific grayscale ultrasound patterns, SWE findings can provide more specificity to imaging findings and probably can help to reach an accurate diagnosis.</p>