To resolve the problem of ageist attitudes in organizational contexts, the psychological processes that contribute to their endorsement must be investigated. We suggest that lay theories of aging (essentialist beliefs about cognitive aging, EBCA), fixed versus growth mindsets, and lay theories of time (LTT, perceptions of time as change versus. repetition) represent a set of beliefs linked to ageist attitudes toward older workers. We also propose that relationships between these beliefs and ageism are mediated by stereotypical perceptions of older workers. In a pilot study, we constructed a measure of ageist attitudes toward older workers (AATOW). In the main study, we surveyed 166 younger workers (18–30 years old, employed full‐time), measuring EBCA, mindsets, LTT, age‐related stereotypes, and AATOW. The results demonstrated that there were significant relationships between EBCA, fixed mindset, LTT, and ageist attitudes. The relationships between EBCA and ageism, and mindsets and ageism were mediated by perceptions of older workers as not adaptable, while the relationship between LTT and ageism was not mediated by age‐related stereotypes. Implications for organizational efforts to nurture an age‐inclusive intergenerational workforce are discussed.