Although the Marijuana Problems Index (MPI) is widely used in studies with college student samples to reflect a unidimensional measure of cannabis-related problems, no studies have assessed the psychometric properties of the MPI in a college student population. The present study sought to resolve this gap in a sample of 879 college students reporting past-year cannabis use. Confirmatory factor analyses were used to test the factor structure of the unidimensional 23- and 18-item MPI and measurement invariance across gender. Bivariate correlations between the final factors, cannabis use history/frequency, and other substance use outcomes were used to examine concurrent and discriminant validities (i.e., vs. noncannabis outcomes). The 18-item (but not the 23-item) MPI demonstrated good model fit, measurement invariance across gender, adequate internal reliability, as well as concurrent and discriminant validities. Results support the use of the 18-item MPI over the 23-item MPI for conceptualizing problematic cannabis use, including the testing of gender-specific differences, among college students. Findings also reinforce the importance of evaluating the psychometric properties of widely used measures across samples. (PsycInfo Database Record (c) 2022 APA, all rights reserved).