This study addresses the relative contribution of social capital and engagement in activity to life satisfaction and quality of life among older Europeans. It examines data from respondents aged 50 and older from the fourth wave of the Survey of Health, Ageing and Retirement in Europe (N=57,234). Employing hierarchical OLS regressions, the findings show that social network ties and activity participation are both related to positive well-being. However, consideration of their interaction reveals that the association between activity participation and well-being varies according to the extent of social capital. Respondents without meaningful social ties benefit most from engagement in a greater diversity of activities. In contrast, respondents with a greater number of social ties experience relatively fewer gains in well-being from activity participation. Thus, it may not be activity, per se, that improves the quality of late life, but rather the social components of the activities in which older adults are involved.