There is a growing recognition that community engagement generates spillover effects, though few empirical analyses have accounted for these often intangible and nonlinear impacts. In the broader political economy of disaster risk reduction (DRR), spillovers present participatory research and practice with opportunities for leveling the resource arguments that currently favor deficit-based communications. A central, unexplored hypothesis of participatory research is as follows: If spillovers result from some forms of community engagement, affecting change in participants and non-participants, then the associated costs of community engagement may be justified by the value of changes that spillover. The possibility of spillovers, while enticing, is hampered by present gaps with regard to the ability to design, implement, and measure targeted spillovers. More simply, spillovers likely follow all social relations, but the ability to target specific outcomes following participation remains presently unknown. Focusing on flood risk reduction in Melbourne, Australia, the community engagement for disaster risk reduction (CEDRR) project utilized “relationship building” to test whether efforts to support flood risk reduction also resulted in spillovers to other aspects of participants’ lives, including to non-participants. To analyze this theoretical possibility, we partnered with a senior citizens’ organization: The University of the Third Age (U3A). Within DRR, senior citizens are often portrayed as inherently vulnerable; while within the aging literature, loneliness and isolation are shown to be key detriments to “successful aging”. The relationship-building methodology, then, aligns with both community engagement and successful aging literatures, enabling an analysis of targeted spillovers related to risk reduction actions and successful aging. Engagements on the topic of flood risk were analyzed to determine whether they had spillover effects on participants’ flood risk actions or on their successful aging outcomes. Findings from 45 remote survey-interviews and 30 follow-up engagements demonstrate that relationship building is an enjoyable form of community engagement able to promote learning, skill development, and intellectual risk-taking (i.e., elements of successful aging). In addition to successful aging, relationship building also contributed to household flood risk reduction behaviors, as well as initiating spillovers to non-participants. These exploratory findings suggest an under-accounted impact of participatory flood risk reduction, which suggests a need to broaden the measurement of “impacts” to include the benefits that spillover to other risk contexts and/or to other individuals.