Background: Breast cancer is a leading cause of cancer-related deaths among women worldwide. In Pakistan, it is diagnosed at a younger age compared to Western populations. Early and accurate detection is crucial for timely treatment and improved survival rates. Bmode ultrasound is commonly used for evaluating breast lesions, but its diagnostic accuracy varies. ‘This study aimed to assess the effectiveness of B-mode ultrasound’ in detecting breast cancer by comparing its findings with histopathology, the gold standard for diagnosis. Methods: A cross-sectional validation study was conducted at the Department of Diagnostic Radiology, Women and Children Hospital Abbottabad, from January 2023 to January 2024. Total 124 patients with suspected breast cancer were included using non-probability consecutive sampling. All patients underwent B-mode ultrasound, followed by a biopsy for histopathological confirmation. ‘The diagnostic accuracy of ultrasound was evaluated in terms of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy’. Data analysis was performed using SPSS version 20. Results: The mean age of participants was 38.98 years (range: 22–60 years). Histopathology confirmed breast cancer in 86.3% of cases, whereas B-mode ultrasound detected malignancy in 55.6%. The overall sensitivity of ultrasound was 64.49%, specificity was 100%, PPV was 100%, and NPV was 30.91%. The diagnostic accuracy of B-mode ultrasound was 69.35%. Age-stratified analysis revealed that ultrasound performed best in the 41 to 60-year group, with a sensitivity of 76.47% and accuracy of 81.82%, while its accuracy was lower in younger patients. Conclusion: B-mode ultrasound is a useful tool for detecting breast cancer, particularly in older patients. However, its lower sensitivity and NPV indicate that it should not be used as a standalone diagnostic method. Histopathological confirmation remains essential, especially in younger patients where ultrasound alone may not be sufficient for an accurate diagnosis. These findings highlight the need for a combined diagnostic approach to improve early breast cancer detection.