Importance: Suicidal ideation and suicide attempt (suicidality) are common in adolescence and a public health concern. Childhood depression is a key risk factor for later suicidality and often co-occurs with irritability. No study to date has examined the joint association of depressive mood and irritability during childhood with later suicidality. Objective: To investigate the association of childhood irritability and depressive/anxious mood profiles with adolescent suicidality. Design, Setting, and Participants: This population-based cohort study included 1430 participants in the Quebec Longitudinal Study of Child Development. Participants underwent assessment yearly or bi-yearly (5 months to 17 years). Data were collected from March 16, 1998, through July 17, 2015. Exposures: Profiles defined by the joint developmental trajectories of irritability and depressive/anxious mood at 6 to 12 years of age. Main Outcomes and Measures: Self-reported past-year suicidality (ie, serious suicidal ideation or suicide attempt) at 13, 15, and 17 years of age. Irritability and depressive/anxious mood were assessed using teacher report 5 times from 6 to 12 years of age. Results: The study included 1430 participants (676 boys [47.3%] and 754 girls [52.7%]) followed up to 17 years of age. Group-based multitrajectory modeling identified the following profiles: combined no irritability and low depressive/anxious mood with low irritability and low depressive/anxious mood (831 [58.1%]; reference group), moderate irritability and low depressive/anxious mood (353 [24.7%]), high depressive/anxious mood only (94 [6.6%]), and high irritability and depressive/anxious mood (152 [10.6%]). Children with high irritability and high depressive/anxious mood reported higher rates of suicidality (25 of 152 [16.4%]) compared with the group with the lowest symptom levels (91 of 831 [11.0%]). In logistic regression analyses, the high irritability and depressive/anxious mood profile (odds ratio [OR], 2.22; 95% CI, 1.32-3.74; number needed to be exposed [NNE], 18) was associated with suicidality. To a lesser extent, the moderate irritability and low depressive/anxious mood profile was also associated with suicidality (OR, 1.51; 95% CI, 1.02-2.25; NNE = 48). The high depressive/anxious mood only profile was not associated with later suicidality (OR, 0.96; 95% CI, 0.47-1.95; NNE = -320). The high irritability and depressive/anxious mood profile was associated with a higher suicidal risk compared with the depressive/anxious mood only profile (OR, 2.28; 95% CI, 1.02-5.15). Girls with the high irritability and high depressive/anxious mood profile had higher risk for suicidality (OR, 3.07; 95% CI, 1.54-6.12; NNE = 5). Conclusions and Relevance: Children with high irritability and depressive/anxious mood and, to a lesser extent, with moderate irritability only had a higher suicidal risk during adolescence compared with children with low symptom levels. Early manifestation of chronic irritability during childhood, especially when combined with depressive/anxious mood, may be associated with an elevated risk for adolescent suicidality. The putatively causal role of irritability should be investigated.< Réduire