The primary aim of this study was to test the effect of a Protection Motivation Theory (PMT)-based patient education intervention on physiotherapy patients' beliefs about their injury and physiotherapy, intentions to adhere, rehabilitation adherence, and ankle function. A secondary aim was to explore the relationships between the patients' injury and physiotherapy beliefs, intentions, adherence behaviours, and ankle function. A randomized controlled trial was undertaken in New Zealand; 71 people with ankle sprains were allocated to either PMT present video information or two control groups (non-PMT information about ankle sprains and no formal information) before commencing their course of physiotherapy. The two information groups watched a video about ankle sprains and physiotherapy before answering the Beliefs about Ankle Sprains and Physiotherapy Scale and behavioural intentions questionnaires that measured the PMT constructs. Adherence was assessed at each treatment and ankle function was measured before and after the physiotherapy program. After viewing the video, the PMT present information group's beliefs about severity, vulnerability, and response efficacy were significantly higher than the other two groups. The groups did not differ significantly on their self-efficacy, intentions, rehabilitation adherence, and post-physiotherapy program ankle function. Significant correlations existed between the patients' PMT-based beliefs and intentions, intentions and adherence, and adherence and post-physiotherapy ankle function. With the exception of self-efficacy, the findings indicate that persuasive information grounded in PMT does enhance physiotherapy patients' beliefs about their injury and treatment.