Purpose Despite increasing awareness of high rates of physical illness and poor lifestyle behaviours among patients with a history of suicidality (suicidal ideation and behaviours), there is little research on specific lifestyle factors that are potentially problematic for this group. This paper aims to explore the relationship between frequency of deliberate self-harm and certain lifestyle factors, including balanced meals, eating breakfast, consumption of 'unhealthy' food, weight, exercise, substance and alcohol use, smoking and social support, in a cohort of patients who present to the Emergency Department (ED) with suicidality. Methods From 2007-2016, data from lifestyle and mental health measures were collected from 448 attenders at an outpatient clinic for suicidal behaviour following an ED presentation. Lifestyle behaviours (from Fantastic Lifestyle Checklist) and mental health (from Depression and Anxiety Stress Scale, clinical diagnosis and number of previous deliberate self-harm episodes) were measured on arrival. The associations between lifestyle variables and mental health outcome measures were examined. Results Gender, age, depression symptoms, poor diet, and smoking were all associated with a higher average number of DSH episodes. There were nonsignificant positive trends between all the other poor lifestyle behaviours and deliberate self-harm. There was no association between deliberate self-harm episodes and diagnosis of depression or anxiety disorder. In a multiple linear regression model the only factors that remained significant were age, smoking and eating balanced meals. Conclusion In this sample of patients with suicidal behaviour, balanced meals and smoking were the lifestyle behaviours that were found to have the strongest independent association with repeated deliberate self-harm. We suggest that asking two simple questions about current smoking and balanced meals has the potential to direct the focus on modifiable lifestyle behaviours with important long term implications for individuals and public health implications for the group of people presenting with suicidality.