Commonalities and complementarities among approaches to conservation monitoring and evaluation (MandE) are not well articulated, creating the potential for confusion, misuse, and missed opportunities to inform conservation policy and practice. We examine the relationships among five approaches to conservation MandE, characterizing each approach in eight domains: the focal question driving each approach, when in the project cycle each approach is employed, scale of data collection, the methods of data collection and analysis, the implementers of data collection and analysis, the users of MandE outputs, and the decisions informed by these outputs. Ambient monitoring measures status and change in ambient social and ecological conditions, independent of any conservation intervention. Management assessment measures management inputs, activities, and outputs, as the basis for investments to build management capacity for conservation projects. Performance measurement assesses project or program progress toward desired levels of specific activities, outputs, and outcomes. Impact evaluation is the systematic process of measuring the intended and unintended causal effects of conservation interventions, with emphasis upon long-term impacts on ecological and social conditions. Systematic review examines existing research findings to assess the state of the evidence regarding the impacts of conservation interventions, and to synthesize the insights emerging from this evidence base. Though these five approaches have some commonalities, they complement each other to provide unique insights for conservation planning, capacity-building, adaptive management, learning, and accountability. Ambient monitoring, management assessment, and performance measurement are now commonplace in conservation, but opportunities remain to inform conservation policy and practice more fully through catalytic investments in impact evaluations and systematic reviews.