Background: Though motivational interviewing (MI) has demonstrated efficacy in a range of behaviour change settings, effectiveness will require successful integration into everyday practice. This study examines implementers’ views on delivering MI within an exercise referral scheme and consistency of consultations with MI before and after a 2-day workshop. Method: Semi-structured interviews were conducted with 27 exercise professionals and 10 area coordinators delivering the Welsh National Exercise Referral Scheme (NERS), and the MI trainer. Eleven professionals provided consultation recordings before and 6-months after training, coded for fidelity using the Behaviour Change Counselling Index. Results: The workshop was well received by most, triggering increased recognition of potential motivational roles of consultations. However, some cited difficulties combining MI with structured data gathering activities, whilst a minority rejected MI, seeing current practice as effective, or MI as unnecessary because patients were ready to change. Although limited aggregate improvement in practice was observed, substantial improvements were observed in some individuals. Comments on the need for further practice or training were widespread. Conclusions: Efforts to implement MI should ensure that training and structures to provide monitoring and feedback are in place and that activities incorporated within consultations are compatible with MI delivery.