Insomnia is a risk factor for suicidal thoughts and behaviors. The present study examined the role of pre-sleep arousal in this association. Seventy-eight adults (Mage = 24.28, 56% had recent history of suicidal thoughts and behaviors) attended two lab visits over four consecutive days. We tested if generally experienced self-reported pre-sleep arousal explained the association between self-report insomnia symptoms experienced over the past two weeks and past week-suicidal ideation. Results indicated full mediation for pre-sleep cognitive arousal, but not somatic arousal. Pre-sleep cognitive arousal could be a key variable linking insomnia symptoms to suicide risk.