Background: Pediatric abdominal masses are diagnostically challenging due to their diverse etiology and nonspecific presentation, necessitating accurate imaging for proper management. This study aimed to evaluate the imaging spectrum and diagnostic performance of radiological modalities in differentiating benign and malignant lesions. Methods: This prospective observational study was conducted at the Department of Radiology and Imaging, Bangladesh Shishu Hospital & Institute, Dhaka, Bangladesh, from January to December 2025. Ninety pediatric patients with suspected abdominal masses were included and evaluated using ultrasonography as the primary modality, with CT and MRI performed when indicated. Imaging findings were assessed for lesion characteristics and origin, and classified as benign or malignant. Diagnostic performance was analyzed using standard statistical measures. Results: A total of 90 pediatric patients with abdominal masses were evaluated, with most aged 1–5 years (40.0%) and a slight male predominance (57.8%), and abdominal swelling being the commonest presentation (82.2%). Renal origin was most frequent (35.6%), followed by hepatic (22.2%), with solid lesions predominating (66.7%) and all patients undergoing USG (100%), while CT (66.7%) and MRI (20.0%) were used selectively. Wilms tumor was the leading diagnosis (24.4%), and overall diagnostic accuracy was 86.7% with sensitivity 91.1%, specificity 79.4%, PPV 87.9%, and NPV 84.4%. Conclusion: Radiological evaluation, led by ultrasonography with complementary CT and MRI, is highly effective in characterizing pediatric abdominal masses and distinguishing benign from malignant lesions.