ABSTRACT Background According to the community‐based model, caregivers play a major role in the care of patients with chronic mental illness. However, caregivers have little time to attend to their own health needs and tend to ignore their health. Caregivers with healthy lifestyle behaviours are likely to achieve greater physical and psychological well‐being. Aim This study aims to assess the healthy lifestyle behaviours and associated factors for the caregivers of patients with chronic mental illnesses. Methods This cross‐sectional study was conducted at the psychiatry outpatient clinic of a hospital in Northwest Turkey, and the sample consisted of 122 caregivers. Data were collected using both a personal information form and the Healthy Lifestyle Behaviours Scale II. Results The Healthy Lifestyle Behaviours Scale II score of the caregivers was 124.37 ± 28.02. The mean total Healthy Lifestyle Behaviour Score significantly varied depending on the caregiver's education level, income, caregiving experience and burnout experiences, the number of psychiatric hospitalisations of their patients in their lifetime and the perceived financial impact and social impact of their care ( p < 0.05). Conclusion The results suggest that psychiatric nurses should play a more active role in protecting and improving caregivers' health and well‐being by developing psychoeducational programmes that could help caregivers adopt healthy lifestyle behaviours.