Recent research has shown that social anxiety may be related to increased risk for suicidal ideation in teens, although this research largely has been cross-sectional and has not examined potential mediators of this relationship. A clinical sample of 144 early adolescents (72 % female; 12-15 years old) was assessed during psychiatric inpatient hospitalization and followed up at 9 and 18 months post-baseline. Symptoms of social anxiety, depression, suicidal ideation, loneliness, and perceived social support were assessed via structured interviews and self-report instruments. Structural equation modeling revealed a significant direct relationship between social anxiety symptoms at baseline and suicidal ideation at 18 months post-baseline, even after controlling for baseline depressive symptoms and ideation. A second multiple mediation model revealed that baseline social anxiety had a significant indirect effect on suicidal ideation at 18 months post-baseline through loneliness at 9 months post-baseline. Social anxiety did not have a significant indirect effect on suicidal ideation through perceived social support from either parents or close friends. Findings suggest that loneliness may be particularly implicated in the relationship between social anxiety and suicidality in teens. Clinicians should assess and address feelings of loneliness when treating socially anxious adolescents.