Exercise is recommended in clinical guidelines for the treatment of chronic whiplash associated disorders (WAD). However, randomised controlled trials have shown similar effects for comprehensive exercise programs and advice. To date, there is no clear understanding of why some individuals with WAD appear to respond to exercise whilst others do not. The aim of this study was to explore the experiences and self-reported characteristics of people with chronic whiplash identifying as ‘responders’ and ‘non-responders’ to exercise. Semi-structured interviews were conducted with 13 people with chronic whiplash (patients) and seven treating physiotherapists. Patients were asked whether they responded to the exercise program, and what contributed to this. Physiotherapists were asked to share their experiences about the characteristics of people that appear to respond to exercise, and those that do not. An interpretive descriptive approach was selected to facilitate the generation of discipline-specific knowledge. Four themes were generated from patient and physiotherapist interviews, including: (1) the therapeutic relationship, (2) exercise experiences and beliefs, (3) self-efficacy and acceptance, (4) physical and psychological determinants of responsiveness. Responsiveness to exercise is complex and multifaceted. Clinicians may seek to identify the presence of discrete physical impairment(s) (e.g., range of motion restriction), and where present, determine whether targeted exercise results in an immediate and positive response. Clinicians may also focus their efforts on developing aspects of the therapeutic relationship identified as important to patients, such as hope, partnership and rapport.