In recent years, there has been growing attention to the distinction between acute and long-term suicidal risk factors. We have previously characterized an acute, negative affect state, termed the suicide crisis syndrome (SCS), as a marker of near-term suicidal risk. Here, we test whether documented long-term risk factors (i.e., trait vulnerabilities), including perfectionism, impulsivity, chronic substance abuse, insecure attachment, poor social support, and childhood trauma, associate to suicidal phenomena through a pathway of the SCS. A sample of 207 psychiatric inpatients were administered a battery of eight scales, including the Suicide Trigger Scale (STS-3) as a measure of the SCS. While both STS-3 and all trait vulnerabilities were associated with lifetime suicidal ideation and attempts, only STS-3 was related to pre-admission suicide attempts. The STS-3 significantly mediated the effect of each trait vulnerability on lifetime suicidal phenomena (combining ideation and behavior), with the proportion of mediating effect ranging from .29 to .56. Reverse mediation analyses were only significant for insecure attachment, supporting a largely unidirectional mediation effect. The SCS appears to serve as an acute risk factor for suicidal behavior in psychiatric inpatients and may act as a mechanism by which long-term risk factors increase suicidal risk.