Missing persons incidents incur considerable societal costs but research has overwhelmingly concentrated on missing children. Understanding the phenomenon among adults is underdeveloped as a result. We conducted an evolutionary concept analysis of the ‘missing person’ in relation to adults. Evolutionary concept analysis provides a structured narrative review methodology which aims to clarify how poorly defined phenomena have been discussed in the professional/academic literature in order to promote conceptual clarity and provide building blocks for future theoretical development. A systematic literature search identified k = 73 relevant papers from which surrogate terms for, and antecedents, consequences, and attributes of the occurrence of adult missing persons were extracted and analysed. The core attributes of the adult missing person are (i) actual or perceived unexpected or unwanted absence accompanied by an absence of information and (ii) a potential adverse risk outcome as perceived by those left behind. The centrality of mental ill-health in actual adult missing persons cases is not reflected in theoretical development which largely comprises descriptive typologies of variable quality and questionable utility. There is a clear need to shift research emphasis towards clinical and psychological domains of inquiry in order to further advance the field of adult missing persons research.