Suicide is a leading cause of morbidity, yet a significant challenge to receiving adequate support is an unwillingness to disclose mental health issues. The current study explores reasons for nondisclosure among emergency personnel, a population at risk of developing mental health problems. Twenty-nine police, ambulance, and fire and rescue agencies from around Australia participated in a mental health and wellbeing survey (N = 14,536, male = 60.5%, 52.0% over 45 years of age, heterosexual = 92.5%). Rates of mental health issues and perceptions of stigma were compared between participants who answered suicide-related questions and those who preferred not to say. Participants who preferred not to answer suicide-related questions (n = 1,098) reported higher rates of psychological distress (symptoms of depression and anxiety), and lower wellbeing and social support, than those who reported suicidal thoughts (n = 1,966) or no suicidal thoughts (n = 11,472). Perceptions of mental health stigma within the workplace, and regarding one's own mental health, also tended to be higher among nonresponders. Imputing their responses based on this survey information resulted in notably higher rates of estimated suicidal thoughts, plans, and attempts. Allowing for nondisclosure in self-report measures of suicide may provide more accurate prevalence estimates and facilitate identification of individuals most at risk of suicide. Addressing stigma in the workplace and also regarding one's own mental health issues may act to improve disclosure of suicidal thoughts and adaptive help-seeking behaviors.