Psoriasis is a common chronic skin condition, which is an immune‐related hyperproliferative disorder. Among the different treatments for psoriasis, statins have been found to reduce the severity of the disease. Accordingly, fluvastatin and simvastatin are known to have anti‐inflammatory effects by inhibiting inflammatory cytokines and lymphocyte function. Narrowband ultraviolet B (NB‐UVB) is known as an effective and safe modality for psoriasis treatment. In this double blind, randomized controlled trial, we investigated the efficacy and safety of adding simvastatin to NB‐UVB phototherapy in patients with psoriasis. Forty‐eight patients with psoriasis undergoing NB‐UVB phototherapy were randomly divided into placebo groups; one received oral simvastatin, and the other received a placebo for 12 weeks. Psoriasis severity was assessed with the Psoriasis Area and Severity Index (PASI) and Dermatology Life and Quality Index (DLQI). Both groups showed a significant decline in PASI score after 6 and 12 weeks compared to the baseline. The differences in reducing PASI score and DLQI between the two groups were not significant neither at week sixth nor 12th. In addition, DLQI decreased significantly in the placebo group at week 12th. In contrast with previous studies, we did not find any additional effects for oral simvastatin5 in treating psoriasis with NB‐UVB. Also, an insignificant difference in the improvement of quality of life between both groups was ascertained.