Background: Patients with mental illness have an increased risk of cardiovascular morbidity and mortality compared to the rest of the population, which is partly related to unhealthy lifestyle habits. To individualise lifestyle counselling in primary care, the Swedish-developed Health Dialogue (HD) can be used as an educative tool at recurrent measurement points with the goal to improve non-healthy lifestyle habits. HD has not been aimed specifically at patients with mental illness, and the effect of a systematic approach with repeated HDs in patients with mental illness in primary care has not been previously studied. The aim of this pilot study was to assess the feasibility of the study design for a larger-scale cohort study using repeated HDs focused on the improvement of lifestyle habits in patients seeking primary care due to anxiety, depression, sleeping problems or stress-related symptoms. Methods: Patients were recruited after a visit to a Primary Health Care Center due to mental illness between October 2019 until November 2021 and received a Health Dialogue, including an assessment of cardiovascular risk factors through a Health Curve. Specific feasibility objectives measured were dropout rate, time to follow-up, and risk improvement rate for different lifestyle changes. Results: A total of 64 patients were recruited and 29 (45%) attended a second HD, with a mean follow-up time of 15 months. All participants had at least one elevated cardiovascular risk level on the Health Curve for the assessed lifestyles. Risk level improvement rate was good except for tobacco use. Conclusion: Despite a higher dropout rate than expected, we suggest that the proposed methodology for a full cohort study within general practice of patients with mental illness in primary care is both acceptable to practice and feasible. © 2023, BioMed Central Ltd., part of Springer Nature.