We introduce and empirically evaluate the strategy affordance hypothesis, which holds that individual differences in strategy use will mediate the relationship between performances on a working memory (WM) span task and another cognitive task only when the same strategies are afforded by both tasks. One hundred forty-eight participants completed basic memory tasks and verbal span tasks that afford the same strategies, such as imagery and sentence generation, and completed reading comprehension tasks that afford different ones, such as self-questioning and summarization. Effective strategy use on WM span tasks accounted for variance in the span-memory relationship, but not for the span-comprehension relationship, supporting the strategy affordance hypothesis. Strategy use mediated the span-cognition relationship only when both tasks afforded the same strategies.