Remaining active throughout the lifespan is central to healthy aging. The current study tests a model derived from investment and resource theories that examines the extent to which activities mediate the relationship between individual differences in personality and resources on mental and physical well-being and retirement expectations. A subsample (N = 400; 58% women) of participants from the nationally representative Health and Retirement Study (HRS) was used. Self-reported activities were grouped into 4 broad categories: productive, physical, social, and leisure. Activity variety, operationalized as the number of different activity categories in which a person reported participating over a specified period of time, was also examined. Correlations and path analysis results suggest small but significant effects between personality traits and activity participation, and more consistent effects of personality for predicting activity variety. Personality was also significantly correlated with well-being and retirement expectations as was activity variety. There was limited evidence, however, that activity variety mediated the relationship between personality and resources and mental and physical well-being and retirement expectations as would be predicted by investment theory.