Given the limited research addressing the construct and content validity of single-item and multiple-item measures of political orientation (PO), we investigated the effect sizes in the relationship between PO and variables categorized into multiple dimensions using a meta-analysis of 511 independent effect sizes from 108 articles published from 2012 to 2022. Multiple-item measures of PO that included economic items had a large effect size ( r = .55 ~ .75) in their association with variables in the economic, environmental, and traditionalism dimensions, whereas we found small effect sizes ( r = .23 ~ .24) between single-item PO and variables in the economic and environmental dimensions and a medium effect size ( r = .31) between single-item PO and variables in the traditionalism dimension. Based on the pooled data consisting of all multiple dimensions’ data subsets, we found medium effect sizes ( r = .35 ~ .39) for multiple-item measures of PO and a small effect size ( r = .27) for single-item PO. Our content analysis of 30 multiple-item measures of PO showed that over 80% of multiple-item measures were grounded in US and/or Western countries’ political contexts and samples and 50% of them did not measure economic aspects of PO. We discuss implications for future research.