Background Injury prevention is an important issue for police officers, but the effectiveness of prevention initiatives is dependent on officers' motivation toward, and adherence to, recommended health and safety guidelines. Aims To understand effects of police officers' motivation to prevent occupational injury on beliefs about safety and adherence to injury prevention behaviours. Methods Full-time police officers completed a survey comprising validated psychometric scales to assess autonomous, controlled and amotivated forms of motivation (Treatment Self-Regulation Questionnaire), behavioural adherence (Self-reported Treatment Adherence Scale) and beliefs (Safety Attitude Questionnaire) with respect to injury prevention behaviours. Results There were 207 participants; response rate was 87%. Hierarchical multiple regression analyses demonstrated that autonomous motivation was positively related to behavioural adherence, commitment to safety and prioritizing injury prevention. Controlled motivation was a positive predictor of safety communication barriers. Amotivation was positively associated with fatalism regarding injury prevention, safety violation and worry. Conclusions These findings are consistent with the tenets of self-determination theory in that autonomous motivation was a positive predictor of adaptive safety beliefs and adherence to injury prevention behaviours.