Rationale and Objectives The bright rim sign (BRS) was used as a reliable indicator of anterior talofibular ligament (ATFL) disruption beside other well-known diagnostic criteria. Although this sign can improve accuracy of conventional magnetic resonance imaging (MRI) in diagnosis of ATFL disruption, it was not adequately discussed in the literature. This study aimed to confirm the added diagnostic value of BRS to conventional MRI assessment of ATFL disruption. Materials and Methods A prospective study included 62 patients (47 males and 15 females; mean age, 36.9 ± 12.1 years; range, 17–52 years) with clinically suspected ATFL disruption. All patients underwent MRI and arthroscopy of ankle. MRI images were evaluated for the presence of ligament disruption sign (LDS) and BRS. The patients were classified into 3 groups: group 1 included patients with acute lateral ankle ligament sprain; group 2 included patients with chronic ankle instability; and group 3 included patients with recurring ankle sprain. The diagnostic value of the BRS was evaluated using arthroscopy as reference standard. Results The diagnostic value of both signs together increased overall sensitivity in detecting ATFL disruption to 86.7% compared to 60% when considering LDS alone (p < 0.0001). In group 1 and 3, the sensitivity increased when both signs were considered together compared to LDS alone (p = 0.004 and 0.025, respectively). In group 2, there was a trend toward significance in sensitivity when both signs were considered compared to LDS alone (p = 0.08). Conclusion BRS is a very helpful diagnostic sign in assessment of ATFL disruption when considered conjointly with the LDS.