Despite the far-reaching impact of suicide on our communities, suicide prevention has historically focused on distally related risk factors for suicidality, which gives us an incomplete picture of how someone comes to make a suicide attempt. Instead, our focus needs to extend to research that explains the maintenance and progression from an emotional state to a suicidal crisis. One such factor, rumination, may create or worsen suicidal thinking by amplifying the distress associated with negative thoughts. Ruminative thoughts are often described as difficult to control, and people may think about suicide as an escape from these uncontrollable thoughts. The current study examined the relationship between severity of lifetime suicidal thinking and certain forms of rumination (i.e., brooding, reflection, anger rumination, and suicidal rumination) in a sample of 145 undergraduate students with suicidal thoughts. For each form of rumination that was related to suicidal thinking, we then examined whether that relationship was accounted for by perceived uncontrollability of one’s own thoughts. We found that all forms of rumination were related to severity of lifetime suicidal thinking, as well as heightened perceived inability to control one’s own thoughts. This thought control inability helped account for the relationships between brooding, reflection, and anger rumination with severity of suicidal thinking, but did not play a role in the relationship between suicidal rumination and suicidal ideation severity. Clinicians should be aware of the impact ruminative thoughts may have on suicidal thinking. More research needs to be done to replicate and extend these effects.