Background: Ultrasound (US) is the first radiological modality to examine females with higher suspicion of adnexal lesions owing to its widespread accessibility, affordable cost, and higher sensitivity in mass detection. Magnetic resonance imaging (MRI) offers essential data for the classification of a lot of ovarian masses as neoplastic or non-neoplastic, and benign or malignant. MRI can identify an adnexal mass and plays an essential role as regard to the differentiation between benign and malignant tumours.  Objective: The current study aimed to compare the diagnostic accuracy of Doppler US and MRI in diagnosis of nature of ovarian mass in teenagers. Methods: This was a descriptive prospective study that included 32 patients with 20 years or less and with adnexal mass attending OB/GYN clinic, admitted and prepared for surgery at Mansoura University Hospitals. All patients were examined after explaining of the procedure of transabdominal US or transvaginal US (for married) according to scanning condition and 23 patients had MRI. Results: MRI had 100% sensitivity, 90% specificity, 92.8% accuracy and US achieved 87.5% sensitivity, 96.2% specificity and 91.2% accuracy. Conclusion: There were no significant differences in sensitivity, specificity, and accuracy of Doppler US and pelvic MRI in characterization of ovarian masses in teenagers. MRI should be used for cases when US results are indeterminate or equivocal, in particular when tumour markers are normal.