The goal of this study is to evaluate feasibility and estimate effect sizes of omega-3 fatty acids (Ω3), individual-family psychoeducational psychotherapy (PEP), their combination, and moderating effects of maternal depression and psychosocial stressors in youth with depression. In a pilot 2 × 2 randomized controlled trial, 72 youth (ages 7-14; 57% Caucasian, 57% male) with major depression, dysthymia, or depression not otherwise specified were randomized to 12 weeks of Ω3, PEP+placebo, Ω3+PEP, or placebo. Ω3 versus placebo was double-masked. Evaluators masked to condition assessed depressive severity at baseline (randomization) and at 2, 4, 6, 9, and 12 weeks using the Children's Depression Rating Scale-Revised. Side effects were either absent or mild. PEP was administered with 74% fidelity. Remission was 77%, Ω3+PEP; 61%, PEP+placebo; 44%, Ω3; 56%, placebo. Intent-to-treat analyses found small to medium effects of combined treatment (d = .29) and Ω3 monotherapy (d = .42), but negligible effect for PEP+placebo (d < .10), all compared to placebo alone. Relative to placebo, youth with fewer social stressors responded better to Ω3 (p = .04), PEP (p = .028), and their combination (p = .035), and those with maternal depression responded better to PEP (p = .020) than did those without maternal depression. Remission rates were favorable compared to other studies of psychotherapy and comparable to an existing randomized controlled trial of Ω3; results warrant further evaluation in a larger sample. Ω3 was well tolerated. Active treatments show significantly more placebo-controlled depression improvement in the context of maternal depression and fewer stressors, suggesting that they may benefit depression with a more endogenous than environmental origin.