OBJECTIVES: Active lifestyles are related to higher levels of cognitive functioning. Fewer studies have examined the importance of engaging in different activities (activity variety) for cognitive functioning. Moreover, it is unclear whether activity variety in specific domains (i.e., cognitive, physical, or social) is important for cognitive health. The current study examined whether overall activity variety as well as variety in specific domains relate to cognitive functioning. METHODS: In Waves 2 and 3 of the Survey of Midlife Development in the United States, 3,337 adults reported their activity engagement and completed a cognitive battery. For longitudinal analyses, 2,049 participants were classified into 4 groups based on their rank ordering of activity variety across 9 years (remained high, increased, decreased, or remained low). RESULTS: Cross-sectional analyses revealed that overall activity variety was related to higher cognitive functioning over and above activity frequency; physical and social activity variety each contributed significantly and uniquely to this association. Longitudinal analyses revealed that those with consistently low overall activity variety at both waves had lower cognitive functioning at Wave 3 than those with high activity variety at either wave, after adjusting for cognitive functioning at Wave 2. Those with consistently high or increasing social activity variety had higher cognitive functioning at Wave 3 than participants with low activity variety at both waves. DISCUSSION: Findings suggest that activity variety, particularly in the social domain, is related to concurrent and future cognitive function across adulthood.