Achievement motivation is a well-documented predictor of a variety of positive student outcomes. However, given observed group differences in motivation and related outcomes, motivation instruments should be checked for comparable item and scale functioning. Therefore, the purpose of this study was to evaluate measurement scale comparability and differential item functioning (DIF) in PISA 2015 achievement motivation items across gender and ethnicity using pairwise and multiple-group comparisons. In addition, DIF was investigated in relation to a common base group that reflected the sample average. Results indicated DIF between gender groups and between the base group and female students. For ethnicity, DIF was consistently flagged in pairwise comparisons with Black/African American students and Asian students as well as in base group comparisons. However, the identified DIF had little practical implications. Implications from these findings are discussed, and recommendations for future research are made.