Measures of prosocial behavior can influence policy, legislation, investment, and inform assessments of the overall state of society. Evidence suggests that methods are important in determining these measures. To widen and deepen our understanding of the complex relationship between these items, we compared participation and volunteering data from a national birth cohort study (National Child Development Study [NCDS]) with data from a linked qualitative study, the Social Participation and Identity Study (SPIS). We evaluated the strengths and prosocial behavior content of each and explored possible links between their respective methodologies and participation and volunteering estimates. We found that prompts and probes were associated with higher estimates and narrow filter questions with lower estimates. The SPIS afforded detailed insights into lived experiences and personal narratives of volunteering and participating, whereas the NCDS supported analysis of these behaviors over time and from a lifecourse perspective. Implications for researchers and policy makers are considered.