Objective: Brief Self-Control Scale (BSCS) is the most widely used instrument to assess self-control. The purpose of this reliability generalization meta-analysis was to examine the degree to which consistency reliability coefficients for scores on the BSCS generalize across age groups and languages. Method: We included studies using the BSCS and reporting a Cronbach's alpha coefficient score since January 2018. Results: Our analysis (j = 180; k = 211) yielded an overall Cronbach's alpha value of 0.81 for the unidimensional 13-item BSCS. Moderator analysis showed that reliability scores ranged from 0.71 to 0.81 across age groups and from 0.77 to 0.90 across languages. Conclusions: Though all internal consistency scores fell in either a good or acceptable range, researchers can consider using a child-specific instrument to assess self-control among children. Reliability scores were also higher in Western areas (e.g., North America) than in non-Western countries.