Cognitive decline amongst older people is associated with poor health and lower quality of life. Previous studies demonstrate that retirement is a particularly critical period for cognitive decline and highlight the importance of post-retirement behaviors. Using longitudinal data from the Survey of Health, Ageing and Retirement in Europe, this study examines the effect of information technology usage on cognitive function, focusing on one specific form: internet usage. We demonstrate that post-retirement internet usage is associated with substantially higher scores on cognitive tests. To address the endogenous relationship between cognitive function and IT usage, we use pre-retirement computer exposure as a source of exogenous variation. Our IV results suggest smaller but still substantial moderating effects of IT usage on the cognitive decline of retirees. These results are concentrated amongst people who worked in middle-skill occupations that experienced largescale computerization. More broadly, our results suggest a causal effect of computer usage on the cognitive function of retirees.