Background Previous randomized controlled trials have demonstrated thatomega-3 polyunsaturated fatty acids (n-3 PUFA) are beneficial in reducing symptoms of depression. However, there is limited evidence regarding the influence of dietary n-3 PUFA intake on mood in adolescents drawn from population studies. Objective In the present investigation, we examined the relationship between dietary n-3 PUFA intake on depression symptomatology in a large prospective pregnancy cohort followed for 17 years. Methods Adolescents enrolled in the Western Australian Pregnancy Cohort (Raine) Study completed a Food Frequency Questionnaire to assess dietary fatty acid intake, as well as other dietary factors at age 14 and a fasting blood sample was taken. Participants also completed the Beck Depression Inventory for Youth (BDI-Y) at age 14 (N=1,407) and at age 17 (N=995). Results An inverse relationship was observed between intake of both saturated fat and of n-3 PUFA at age 14 and BDI-Y scores at both 14 and 17 years of age. However, after adjusting for energy(kJ) intake and other lifestyle confounders, the relationships were no longer significant. Conclusions Associations previously reported between n3 PUFA and depressive symptoms may be due to collinearity with other dietary and lifestyle factors.