Cohort and cost-effectiveness studies suggest that measuring variation in genes that influence metabolism of common drugs could improve antidepressant treatment outcomes. Prior randomized trials have yielded inconsistent results. Multicenter randomized double-blind (subject and rater), controlled trial of pharmacogenomic testing among outpatients with nonpsychotic major depressive disorder. Study participants (n = 304) were randomized 1:1 to assay-guided treatment (AGT; N = 151) or treatment-as-usual (TAU; N = 153). Participants and raters were blinded to study arm; unblinded clinicians received results of a pharmacogenomic test and adjusted treatment in light of the test report. Primary outcome was change over 8 weeks in Hamilton Depression Rating Scale (SIGH-D-17). For the primary comparison of interest, change in SIGH-D-17, no significant difference was detected between AGT and TAU at Week 8 (p = .53). Rates of study completion also did not differ between the arms (AGT 92.7%, TAU 92.2% (χ2 = 0.03, df = 1, p = .86). Exploratory analyses suggested significantly fewer individuals experienced worsening of depressive symptoms following AGT, and that treatment concordant with assay results was associated with greater likelihood of remission. Pharmacogenomic testing using a panel of pharmacokinetic and pharmacodynamic variants was not associated with significant improvement in the primary efficacy outcome when providers were unconstrained by the assay results. Further investigation is needed to understand the discordance with cost-effectiveness results and among randomized trials. © 2020 Wiley Periodicals, Inc.