Background: Sexual dysfunction is common among patients with major depressive disorder (MDD). In the CLARITY study, the safety and efficacy of adjunctive pimavanserin, an inverse agonist at 5-HT 2A receptors, were demonstrated when added to existing treatment for MDD. This analysis provides a detailed assessment of the effects of pimavanserin on sexual function from the CLARITY study. Methods: Patients with a diagnosis of MDD in a depressive episode, inadequate response to ongoing antidepressant therapy, and a Montgomery-Åsberg Depression Rating Scale total score >20 were randomized to pimavanserin 34 mg/day or placebo added to ongoing treatment with an immediate revision of all selective serotonin or serotonin-norepinephrine for 5 weeks (Stage 1), and nonresponders (<50% improvement from baseline in Hamilton Depression Rating Scale [HAMD-17]) were re-randomized for an additional 5 week (Stage 2). Effects of pimavanserin on the Massachusetts General Hospital Sexual Functioning Index (MGH-SFI) and HAMD-17 Item 14 (sexual interest) were examined. Results: Among 203 patients (51 on pimavanserin; 152 on placebo), pimavanserin demonstrated significant improvement from baseline to Week 5 on the MGH-SFI (least square [LS]mean difference −0.634, 95% confidence interval [CI] [−0.964, −0.304]; p = .0002; effect size [ES], Cohen's d: .614). Across Stages 1 and 2, the weighted LSmean difference was −0.468 (95% CI [−0.720, −0.216]; p = .0003) for pimavanserin versus placebo. Mean changes from baseline to Week 5 for MGH-SFI Items 1, 2, 3, and 5 and HAMD Item 14 were significantly (p < .05) greater with pimavanserin versus placebo. Conclusions: Adjunctive pimavanserin improved sexual function in patients with MDD. Adding pimavanserin to ongoing treatment for MDD may be especially useful for patients experiencing sexual dysfunction. K E Y W O R D S adjunctive, major depressive disorder, pimavanserin, sexual function