Detecting contingency relationships between causal events allows us to adapt to and control these events. However, research has shown age-related impairments in this ability. The goal of this study was to examine how reduced processing speed in older adults affects contingency learning. Manipulating the time during which to generate the response, to test the limited time mechanism of processing speed, had little effect on contingency judgments. Varying the temporal contiguity of events, to test the simultaneity mechanism of processing speed, affected young adults’ contingency judgments. Older adults’ judgments were less accurate overall, and young adults’ judgments were similarly less accurate when there was less temporal contiguity of events. These findings lend support for a processing speed theory of contingency learning.