Age is an important dimension that is used by people to categorize others. Age-based discrimination is directed toward specific age groups (young and old). In spite of their importance, attitudes toward the elderly have hardly been studied from a cross-country perspective. The fourth round of the European Social Survey (ESS) from 2008-2009 offers, for the first time, the opportunity to study ageism and attitudes toward age groups from a cross-country perspective (European Social Survey Round 4 Data, 2008). However, this opportunity also bears the risk of drawing wrong conclusions, if the scales measuring ageism are not comparable across the countries under study. Such comparisons require measurement equivalence across countries. In the current study, utilizing ESS fourth round data from 29 European countries we examine the cross-country measurement equivalence properties of two concepts that are measured by multiple indicators in the module: (1) competence and warmth and (2) experience of age discrimination. We test for measurement equivalence using two analytical methods: multi-group confirmatory factor analysis (MGCFA) and the alignment optimization. Our findings suggest that cross-country comparisons of these measures are trustworthy. We briefly discuss cross-country differences in competence and warmth and experience of age discrimination. Finally, we underline the importance of testing the cross-group equivalence of measurement instruments before using them in different groups (such as countries) so that meaningful substantive conclusions can be drawn.