Spillover effects are considered important in evaluating the impacts of food, energy and water (FEW) conservation behaviors for limiting global greenhouse gas emissions and climate change. Failure to account for all possible spillovers, or indirect and unintended results of an intervention, not only obscures valuable information pertaining to the dynamic interactions across domains but also results in biased estimates. In this study, we first systematically reviewed articles that investigate the idea that the performance of one pro-environmental behavior influences the conduct of subsequent behaviors(s) from the FEW domains. From our review of 48 studies in the last decade, we note that a big part of the discussion on spillover concerns the nature and direction of causal relationships between individual FEW conservation behaviors. We identify a critical gap in the literature regarding the distinction between spillover effects caused by the interventions as distinct from those caused by the primary behaviors. Next, we conducted a quantitative meta-analysis of the reviewed empirical studies to find a modest but overall positive spillover effect. Finally, we reviewed the theoretical and methodological plurality in the FEW spillover literature using a systemic thinking lens to summarize what is already known and identify future challenges and research opportunities with significant policy implications.