Introduction: This study analysed the psychometric properties of the Reward Probability Index (RPI) in an online Colombian sample with 1129 participants. Method: To conduct a cross-validation study, the sample was randomly divided into two subsamples. An exploratory factor analysis was conducted with the first subsample yielding a two-factor structure. Then, the fit of this two-factor model was tested on the second subsample by conducting a confirmatory factor analysis. Results: This model obtained a good fit to the data and measurement invariance across gender was observed. The RPI also showed good internal consistency according to both Cronbach’s alpha and McDonald’s omega, scoring .88 in both cases. The RPI demonstrated convergent construct validity given its correlations with other related measures such as the Environmental Reward Observation Scale (r = .81), and the full version of the Behavioral Activation Scale for Depression (r = .71). Conclusions: The RPI showed good psychometric properties in this Colombian sample.