The purpose of this research is to investigate the research problem: Why does emergent usage occur in adaptive information systems? Being motivated to explore this phenomenon from the experiential perspective, three research questions were posed: (1) What experiential factors describe emergent usage of adaptive information systems? (2) What generative mechanisms must exist for such emergent usage to be possible?" (3) What explains the relations of the mechanisms to effect emergent usage of such information systems? Emergent usage of adaptive information systems, predominantly accessed with smart mobile devices has become pervasive. The research problem, therefore, arises as a result of the continued under-theorization of emergent usage of adaptive information systems and lack of theory to explain why such usage occurs. To answer the research questions, an intensive single organization case-study, underpinned by critical realism, was deployed. The research explored an adaptive e-financial system developed by the case organization for public use. The research was aimed at identifying the causal mechanisms and the enabling contextual conditions that explain the system's emergent usage and the experiential factors that describe such usage. Multiple sources of qualitative data, namely, participant observation, interviews, and photography were used to collect data between 2012 and 2014. The retroductive data analysis employed a research model which was developed from a theoretical redescription of the phenomenon using a conceptual framework synthesized from literature and theories of complex adaptive systems (CAS) and meta-design. The findings were encapsulated in a concluding model termed, the Technology Emergent Usage Model (TEUM), as the key theoretical contribution of this thesis. TEUM is an explanatory case specific mid-range theory. The theory's relevance is based on its openness to flexible interpretation when applied to different contexts in future research, without making claim to its universality. Other contributions include methodological and practical contributions to highlight an area where there has been little or no empirical research to date. Advisors/Committee Members: Brown, Irwin (advisor), Carlsson, Sven (advisor).