Retirement has been associated with cognitive decline. However, the influence of specific job characteristics like occupational complexity on post-retirement cognitive outcomes is not well understood. Data from the Midlife in the United States (MIDUS) study were used to examine occupational complexity in relation to cognitive performance and cognitive change after retirement. Initial sample included 471 workers between 45 and 75 years of age. At 9-year follow-up (T2), 149 were retired and 322 were still working. All six tasks from the Brief Test of Adult Cognition by Telephone (BTACT) were used. Hierarchical regression with workers at T1 indicated that, controlling for sociodemographic variables, complexity of work with people significantly contributed to explaining variance in overall cognitive performance (1.7%) and executive function (2%). In Latent Change Score (LCS) models, complexity of work with people was the only significant predictor of cognitive change in retirees, with those retiring from high-complexity jobs showing less decline. In conclusion, high complexity of work with people is related to better executive functioning and overall cognition during working life and slower decline after retirement. The finding that more intellectually stimulating work carries cognitive advantage into retirement fits the cognitive reserve concept, where earlier intellectual stimulation brings about lower risks of cognitive problems later. Study results also go along with the unengaged lifestyle hypothesis, whereby people may slip into so-called "mental retirement," leading to post-retirement cognitive loss, which may be most apparent among those retiring from jobs with low complexity of work with people. (PsycInfo Database Record (c) 2021 APA, all rights reserved).