Objective: This study tests a novel, within-person model that reexamines depression and stress as risk factors for suicidal ideation and behavior among adolescent girls with and without sexual/physical abuse histories. Method: This longitudinal study includes data from 220 adolescent girls between 12 and 16 years of age (M = 14.69 years, SD = 1.37; 61% White). At baseline, adolescents reported the presence or absence of prior abuse as part of a clinical interview. At baseline and every 3 months for 18 months, adolescents completed measures of suicidal ideation and behavior, depressive symptoms, and stress. Results: Multilevel models examined within-person mean, deviations from within-person mean, depression, and stress and their interactions with abuse as predictors of suicidal ideation and behavior. In addition to within-person mean depression, higher-than-usual depression (odds ratio [OR] = 1.99) and higher-than-usual stress (OR = 1.53) predicted greater risk of suicidal ideation at each follow-up assessment. Periods of higher-than-usual stress (1 SD increase) and periods of higher-than-usual depression (1 SD increase) were associated with an 82% and 57% increase in the odds of suicidal behavior, respectively, but only among those with abuse histories. Conclusion: Depression, stress, and abuse are well-known risk factors for suicidal ideation and behavior; however, it has been unclear for whom, and when, these factors have their greatest impact. These results show that depression and stress are potent risk factors among those with a history of abuse and that within-person elevations in these risk factors signal increased short-term risk of suicidal ideation and behavior.