The clear reporting of relational and technical principles, skills and processes which underpin intervention delivery in applied sport psychology is often missing, in favour of intervention content. Repeated calls have been made for what has been described as an interface between counselling psychology and sport psychology, to fill this gap (e.g., Andersen & Speed, 2010; Petitpas, Giges, & Danish, 1999; Poczwardowski, Sherman, & Henschen, 1998). More specifically, practitioners might consider immersing themselves in a counselling approach for greater understanding of the therapeutic alliance and its components, arguably the most important predictor of behaviour change in consultation with athletes (Andersen, 2006). While limited guidance exists for applying counselling methods to sport psychology (e.g., Katz & Hemmings, 2009; Murphy & Murphy, 2010), a specific counselling approach with a clear training pathway has yet to be suggested. Motivational interviewing (MI; Miller & Rollnick, 2013) is one counselling approach which contains the relational and technical active ingredients for fostering strong therapeutic alliances with athletes, and immersion in this approach could support practitioners in learning the therapeutic methods required to develop these interpersonal relationships and work from an athlete-centred perspective (Andersen, 2006; Holt & Strean, 2001). Additionally, applied sport psychologists are increasingly reaching beyond the psychological skills training and psychoeducation which have been dominant in the discipline, instead beginning to learn and apply specific psychotherapies, such as rational emotive behaviour therapy (REBT: Wood, Barker, & Turner, 2017) and acceptance and commitment therapy (ACT; Shortway, Wolanin, Block-Lerner, & Marks, 2018). An integration of MI with cognitive behavioural therapy (CBT) is becoming better understood in clinical and counselling psychologies (e.g., Geller & Dunn, 2011; Westra, Arkowitz, & Dozois, 2009), and such an integration may prove fruitful for sport psychology interventions. The purpose of this thesis was therefore to formally propose and explore MI as a valuable, efficacious counselling approach to underpin applied sport psychology practice. Three studies were undertaken in this endeavour. Study one explores the current use and understanding of MI among chartered sport and exercise psychologists in the UK. Findings indicated that certain aspects of the MI approach are being used in sport psychology consultancy, but there are gaps in the knowledge and application of the approach. Study two explores how MI is being applied in sport contexts by a global sample of practitioners who are proficient MI practitioners and trainers. Findings indicate core and auxiliary components of MI are valuable for enhancing intervention work with athletes. Study three outlines the design, implementation and evaluation of an MI for sport psychology workshop series attended by early career sport psychologists. Findings indicate increased MI adherent practice post-training, and perceived value of MI for enhancing applied practice. This thesis concludes that MI presents one counselling approach suitable for integration into sport psychology practice, with the potential to enhance relationships and interventions with athletes.