Abstract Objective To estimate the prevalence, incidence and determinants of suicidal ideation in the multiple sclerosis (MS) population. Methods A sample of 188 subjects were randomly selected from a community-based MS clinic registry and participated in as many as 13 interviews over 6 months. Thoughts of “being better off dead” or of “harming oneself” were assessed using item 9 on the Patient Health Questionnaire, Brief (PHQ-9). Results At baseline, the 2-week period prevalence of suicidal ideation was 8.3%. Over the course of 6 months, 22.1% of respondents reported having such thoughts at least once. Survival analysis incorporating baseline PHQ-8 scores as a covariate confirmed that being age 65 and over (HR=4.3, 95% CI 1.7–11.3) and having lower quartile self-efficacy ratings (HR=3.5, 95% CI 1.5–8.2) predicted suicidal ideation. Lower levels of task-oriented coping (treated as a continuous variable) also predicted suicidal ideation after adjustment for depressive symptoms (p=0.015), as did self-reported bladder or bowel symptoms (HR=2.6, 95% CI 1.1–6.0) and difficulties with speaking and swallowing (HR=2.9, 95% CI 1.3–6.8). Associations with MS symptoms were not confounded by depressive symptoms. Conclusion This study identified several potentially modifiable factors that may be useful for preventing suicide in people with MS.