Introduction: Adnexal masses represent a diverse group of gynaecological conditions with origins in the ovary, fallopian tube, and surrounding structures and are a frequent clinical presentation among women, ranging from benign cysts to malignant tumours. Early imaging-based characterization is crucial for management.

Aim: To compare the diagnostic efficacy of ultrasonography (USG) and magnetic resonance imaging (MRI) in evaluating and differentiating benign and malignant female adnexal masses.

Materials and Methods: A prospective study was conducted over 18 months on 100 patients with suspected adnexal masses. All underwent USG followed by MRI. Imaging findings were evaluated and compared with histopathological results. Data analysis was performed using SPSS; chi-square tests were applied with p<0.05 considered statistically significant.

Results: MRI demonstrated higher sensitivity (94.1%) and specificity (98.7%) compared to USG (88.2% and 96.3% respectively) in identifying and characterizing adnexal pathology especially for correctly identifying benign and malignant lesions by MRI as compared to USG. MRI outperformed USG in lesion characterization and staging, particularly in complex and malignant masses. The mean age of patients was 41.42 ± 7.6 years, with majority in the 31–40 age group. In cases where USG findings were indeterminate, MRI provided definitive characterization of lesions.

Conclusion: USG remains the first-line modality due to accessibility and cost-efficiency. However, MRI offers superior accuracy, especially in indeterminate cases, making it indispensable in complex or unclear adnexal lesions. MRI's multiplanar capability and tissue characterization provide critical information for preoperative planning and may prevent unnecessary surgery in benign lesions.