Mental illness is a prevalent and extraordinarily complex phenomenon. Psychologists have developed distinct approaches toward understanding and treatingmental illness, rooted in divergent epistemology. This introduction to the Special Issue on Clinical Psychological Science and Practice provides a brief overview of the scientist-practitioner gap, and explores one step (of many) toward bridging this divide. Seven compelling case illustrations featured in this Special Issue apply empirical findings to case formulation, treatment selection, and assessment across complex and varied clinical presentations. This issue thereby demonstrates the feasibility of integrating research and clinical expertise in mental healthcare. (C) 2017 Wiley Periodicals, Inc.