Backgrounds There are contradictory evidence about the effect of statins on depression. This 6‐week‐randomized placebo‐controlled clinical trial assessed the efficacy and safety of lovastatin as an adjuvant agent for treating major depressive disorder (MDD). Methods The participants were 68 patients with MDD according to DSM‐IV diagnostic criteria. The sample was randomly allocated into fluoxetine (up to 40 mg/day) plus lovastatin (30 mg/day) group or fluoxetine plus placebo group. Hamilton Depression Rating scale was used to measure depression score at baseline, week 2, and week 6. Results Both groups showed a significant decrease of depression score on the Hamilton Depression scale. However, the treatment group decreased depression score more than placebo group [12.8(6.3) vs. 8.2(4.0), t = 3.4, df = 60, P < .001]. Any serious adverse effect was not found. Discussion These results suggest that lovastatin as an adjuvant treatment may be effective for treating patients with MDD.