Research on the average reliability and factors that affect the reliability of loneliness scales has been restricted to unidimensional measures. A reliability generalization (RG) study was conducted for a multidimensional loneness measure, that is, the Loneliness and Aloneness Scale for Children and Adolescents (LACA). Multilevel meta-analyses were performed on 79 studies that comprised 92 samples (for a total of 41,076 participants). Average reliability (Cronbach’s alpha) across samples was good (i.e., .80 or above) for all four subscales. Studies with higher sampling quality yielded slightly higher alphas for one of the subscales (i.e., Parent-related loneliness). For adolescents, as compared to children, alphas were somewhat lower for three of the four subscales and higher for the Affinity for aloneness subscale. Suggestions for future research are outlined. From a reliability perspective, the LACA is a good option for researchers who want to use a multidimensional loneliness measure with children and adolescents.