Comorbidity between bipolar disorder (BD) and obsessive-compulsive disorder (OCD) is fairly common, and the treatment of these conditions when comorbid is challenging. Serotonin reuptake inhibitors, the first option for treatment of OCD, can worsen BD symptoms, and mood stabilizers are generally not efficacious for OCD. Our goal in this article is to assess the clinical effectiveness of pharmacotherapies for comorbid BD-OCD in adults. We searched the Medline, Embase, and Cochrane Central Register of Controlled Trials databases on April 30, 2017, and we also searched the reference lists of identified articles. Studies published beginning January 1, 2007 were included, without language restrictions. Narrative and systematic reviews, letters to the editor, and book chapters were excluded. Two authors independently assessed the quality of the studies and extracted data. Seven studies met our inclusion criteria. Findings from double-blind, randomized, placebo-controlled trials were pooled for analysis. Findings from this pooled analysis indicated that augmentation of mood-stabilizer treatment with glutamate modulator agents (topiramate or memantine) may favor full response of obsessive-compulsive symptoms (risk ratio: 2.62, 95% confidence interval: 1.45-4.74) in patients with BD type I and OCD in the manic phase, and that it does not significantly induce adverse effects (risk ratio: 1.26, 95% confidence interval: 0.53-3.01). Results of a narrative synthesis of observational studies indicated greater efficacy of mood-stabilizer treatment, with serotonin reuptake inhibitors less used. Findings from studies employing different designs were not compared, and our results should be interpreted cautiously.