Greater childhood adversity predicts a higher likelihood of later self-injurious thoughts and behaviors (SITB). There is little research focused on whether the timing of childhood adversity predicts SITB. The current research examined whether the timing of childhood adversity predicted parent- and youth-reported SITB at age 12 and 16 years in the Longitudinal Studies of Child Abuse and Neglect (LONGSCAN) cohort (n = 970). We found that greater adversity at age 11–12 years consistently predicted SITB at age 12 years, while greater adversity at age 13–14 years consistently predicted SITB at age 16 years. These findings suggest there may be sensitive periods during which adversity may be more likely to lead to adolescent SITB, which can inform prevention and treatment.