Background: The incorporation of spillover effects in health economic research is recognized by regulatory agencies as useful for valuing health interventions and technologies. To date, spillover effects are not universally used within economic evaluations and conceptual definitions of spillover effects are vague within the context of health economics research. Materials & methods: In an effort to enhance awareness of spillover effects for health economic evaluations, a concept analysis using Walker and Avant's approach was performed to elucidate the key attributes, definitions, antecedents and consequences of spillover effects across a range of disciplines. Results: Key attributes included lack of intention, positive and negative impacts, and two entity/domain involvement. Antecedents included an initial action and desired outcome. Consequences involved spillovers across industries, work life to personal life domains, patient to family member domains and across healthcare markets. Conclusion: The analysis provides greater clarification around the dimensions of spillover effects and reveals opportunities to enhance methodological approaches to assessing spillovers.