To investigate whether a positive transition into retirement may be associated with later cognitive aging, we included a subset of 4,926 Nurses' Health Study participants who retired from work at ages 60-69, then provided a subjective assessment of the change in overall quality of life (QOL) with retirement. Subsequently (range: 1 month to 4.7 years later), when all were aged 70+ years, they completed a baseline telephone cognitive battery evaluating global cognition, episodic memory, and executive function. They had up to three follow-up cognitive assessments. Controlling for various occupational factors before retirement and socioeconomic, lifestyle, and health-related factors as of the baseline cognitive assessment, we used generalized linear models for repeated measures to estimate mean differences in rates of cognitive decline across categories of QOL transition at retirement: "worse", "same", or "better". Over a median 6 years of follow-up, the global cognitive score change was -0.123 on average. Compared with women who reported no change in QOL at retirement (31%), women who reported improvement (61%) showed a significantly slower rate of cognitive decline (difference = +0.011 95% CI = 0.004, 0.019). This mean difference was equivalent to that observed between women who were 2 years apart in age. No significant differences in cognitive decline rates were observed for the women who reported worsened QOL (8%). Secondary analyses to address possible reverse causation showed robust associations. A positive transition into retirement was associated with better maintenance of cognitive function over time in aging women. These findings need to be replicated in other populations.