Objectives An acquired melanin-related hyperpigmentation that occurs in sun exposure areas is Melasma which presents as gray-brown ridges and macules with prominent margins on the skin. The aim of this assay was to assess the formulation and efficacy of topical Dorema ammoniacum among Melasma patients. Methods This study was a 30 days double-blind, randomized clinical trial in Melasma with a placebo group. The study was carried out on 49 patients with Melasma attending Haji Daii Nursing Center in Kermanshah, Iran. Optimized topical formulation of D. ammoniacum gum extract was prepared by evaluating the characteristics of different topical formulations of this plant. Mean Melasma severity index (MMASI) instrument was applied to assess the product effectiveness and to determine the skin stains. Patients were pursued to receive the treatment throughout the 30 days trial. This scaling was accomplished before the intervention and 30 days after the use of the herbal product. To analyze the quantitative variables, t-test and Mann–Whitney test were evaluated by SPSS 21 software, and p-value <0.05 was considered as the statistically significant. Results The survey was performed on 40 female subjects (81.6%) and nine male subjects (18.4%) with the mean age of 32.18 ± 8.69. According to the results, the mean MSI in the drug group was significantly lower than before treatment and decreased from 86.98 ± 69.48 to 31.03 ± 32.62 (p-value <0.05). Conclusions In compliance with findings this survey revealed a positive effect of the cream formulation of D. ammoniacum extract on Melasma. As it was represented no side effects, this formulation is appropriate for the treatment of Melasma.