One of the most widespread beliefs about the occurrence of age discrimination is that it is attributable to age stereotypes. However, the mere activation of age stereotypes is by no means a sufficient condition for the occurrence of age discrimination. Accordingly, the aim of this chapter is to critically review the hypothesis that age stereotypes cause age discrimination considering their conceptual relatedness as well as empirical evidence. It is important to acknowledge that age discrimination and age stereotypes are domain-specific phenomena. Besides taking contextual aspects into account, we also consider the perspectives of both the actor (i.e., the discriminating person) and the perceiver (i.e., the older adult who is being discriminated against and/or perceives age discrimination) to better understand the stereotype-discrimination association. Regarding the actor’s perspective, several studies identified moderators of the relationship between age stereotypes and age discrimination. This perspective can be complemented by considering that older adults themselves also hold age stereotypes that affect their interpretation of other peoples’ behaviour towards them and even their own behaviour. Accordingly, a reciprocal relation between the stereotypes held by both parts is easily conceivable where their expectations and behaviours mutually reinforce each other. In order to understand the relations between age stereotypes and age discrimination it is necessary to consider personal characteristics and contextual constraints on both parts, and to acknowledge the added complexity and domain-specificity of the relations between age stereotypes and age discrimination in real life interactions.