Abstract: After 45 years of strong development, global application and ongoing criticism, the contours of what constitutes NLP remain vague, to insiders and outsiders alike. NLP experts use more or less different definitions and criteria for the tools, techniques and foundation principles of NLP. This situation has made it nearly impossible to satisfy the request for research evidence of NLP’s effectiveness in coaching. The purpose of this paper therefore is to commence a discussion of the challenges facing NLP in gaining legitimacy as a coaching approach without an evidence base. The paper critiques the extant literature on NLP coaching, and briefly reviews wider literature of NLP evidence in other contexts, notably the therapy world. This paper offers a summary of and critique of a recent Delphi Poll conducted to identify which of the tools, techniques and theoretical frameworks are considered to be NLP. The paper discusses the challenges for NLP evidencing its effectiveness in coaching and proposes empirical outcome based research utilising the core principles, skills, tools and techniques that have gained consensus in this Delphi Poll.