Background Lifestyle interventions are important to improve the mental and physical health outcomes of people with mental illness. However, referring patients to lifestyle interventions is still not a common practice for mental healthcare professionals (MHCPs) and their own lifestyle habits may impact this. The aim of this study was to investigate MHCPs' personal lifestyle habits, their lifestyle history and referral practices, and if these are associated with their lifestyle habits, gender, and profession. Methods In this cross-sectional study, an online questionnaire was distributed across relevant MHCP's in The Netherlands. Ordinal regression analyses on lifestyle habits, gender, profession, and lifestyle history and referral practices were conducted. Results A total of the 1,607 included MHCPs, 87.6% finds that lifestyle should be part of every psychiatric treatment, but depending on which lifestyle factor, 55.1-84.0% take a lifestyle history, 29.7-41.1% refer to interventions, and less than half (44.2%) of smoking patients are advised to quit. MHCPs who find their lifestyle important, who are physically more active, females, and MHCPs with a nursing background take more lifestyle histories and refer more often. Compared to current smokers, MHCPs who never or formerly smoked have higher odds (2.64 and 3.40, respectively, p < 0.001) to advice patients to quit smoking. Conclusions This study indicates that MHCPs' personal lifestyle habits, gender, and profession affect their clinical lifestyle practices, and thereby the translation of compelling evidence on lifestyle psychiatry to improved healthcare for patients.