The Alabama Parenting Questionnaire-9 (APQ-9) is a widely used brief measure of parenting behaviors. However, the reliability coefficients of the three APQ-9 subscales vary substantially. A reliability generalization meta-analysis was conducted on the three APQ-9 subscales to (a) estimate mean internal consistency reliability values and (b) examine the sources of variance. A total of 113 coefficient alphas from 31,572 informants, across 32 studies were included in this meta-analysis. Results showed acceptable mean α values (.84 for positive parenting, .66 for inconsistent discipline, and .70 for poor supervision subscales). Moderator analyses results found that differences in coefficient αs of the three subscales were influenced by numerous variables including administration format, country, language version, population, the mean and standard deviation of scores, and sample size. Our findings support the utility of the parent-report APQ-9 as a useful measure of parenting behaviors. Future research direction is also discussed. (PsycInfo Database Record (c) 2021 APA, all rights reserved).