Despite extensive use in research assessing myths around male sexual victimization, the factorial structure of Melanson’s 1999 Male Rape Myth Scale [MRMS] was never psychometrically validated, meaning the relevance of scale items and dimensionality remained untested. Recruiting a nationally representative sample of 4152 UK adults, dimensionality and construct validity of the 22-item MRMS and a modified 19-item shortened version (MRMS-SV) were investigated using Confirmatory Factor Analysis (CFA). Analysis was conducted separately for the complete, male only (n = 2006), and female only (n = 2146) samples. Results indicate scores are best captured by a unidimensional solution across all samples tested, using the modified 19-item MRMS-SV version. Excellent internal reliability was observed among each sample. Research using the MRMS-SV can be confident in the scale’s unidimensional validity.