Improving the performance of Poverty Alleviation Interventions (PAIs) is crucial to justify the resources they consume, and for how they pitch and then address aspirations of the beneficiary community. In this paper, we work from the accepted premise that engagement response of the beneficiary community is central to the performance of such interventions. ‘Willingness to engage’ and ‘ability to engage’ are articulated as two dimensions that shape this response with examples and a discussion on how research has related with these constructs. We argue how willingness and ability have an evolving interface over the PAI lifecycle, and examine a drinking water and sanitation PAI in East India. Our propositions from this inductive study culminate in a theory of community response mediation. We suggest that willingness and ability fully mediate each other's effect on community engagement response with implications for how PAIs are resourced, designed and delivered.