This article reviews the value of magnetic resonance imaging (MRI) for the diagnosis of ovarian tumors especially when ultrasonography is indeterminate. Although ultrasonography is the first imaging technique used to investigate suspected pelvic masses, it has a limited capacity for tissue characterization. In addition to morphological characteristics, many tissue parameters such as T1, T2, perfusion, and diffusion contribute to signal intensity, so MRI is able to identify various types of tissue contained in pelvic masses. Magnetic resonance imaging helps to locate large solid masses and to distinguish benign from malignant ovarian tumors, with an overall accuracy of 88% to 93% for the diagnosis of malignancy. The aims of this review are 3-fold. First, we review state-of-the-art and usual MRI techniques and published findings. Second, we recall the MR features most useful for assessing the main ovarian tumors. Finally, we discuss the relevance of various features for distinguishing between benign, borderline, and invasive ovarian tumors.