Divorce has been identified as a risk factor for suicide. However, little research has been conducted on the time trajectory of the influence of relationship separation on suicidal outcomes. This study aimed to assess the effects over time of relationship breakdown and separation on suicidality. Data were drawn from 6616 Australian adults participating in the PATH through Life Project, a population-based longitudinal study. Suicidal ideation was reported by 406 participants (6.1%), and 99 (1.5%) reported a suicide plan or attempt in the past year. The effects of separation on suicidality were strongest soon after separation, with a nearly three-fold increase in ideation (adjusted OR=2.73, p<0.001) and an eight-fold increase in plans/attempts (adjusted OR=7.75, p<0.001) in the two years following separation, gradually diminishing subsequently. The period up to four years before a separation was also found to be a time of increased risk for suicidal thoughts and behaviours, while marriage was protective. Separation is a strong risk factor for suicidality and mental health services should target recently separated individuals.