Background: Management of cold-associated cough is a challenging aspect of supportive care for the common cold for pediatricians and parents worldwide. Herbal compounds have traditionally been used for the treatment of cold-related cough. Among these compounds, Zataria multiflora (ZM) has been found to be effective for cough relief. Objectives: The aim of this study is to compare a thyme mixture with diphenhydramine in the treatment of cold-related cough in a double-blind, randomized, clinical trial. Patients and Methods: A total of 52 pediatric patients (2 -12 years old) with common colds were included in the study. The patients were randomly divided into two treatment groups: one group received diphenhydramine compound and the other received ZM syrup, each for five days. The severity of cold-related symptoms and the efficacy of each drug were determined seven days later by asking the parents to complete a prepared questionnaire. sedation, sleepiness, a four-point scale of cough status, and a two-point scale of consumption convenience were also evaluated in these questionnaires. Results: Our results showed that sedation and sleepiness occurred in 30.8% and 19.2% of the patients in the diphenhydramine and ZM groups, respectively (P = 0.54). Also, 65.4% and 84.6% of the patients in the diphenhydramine and ZM groups, respectively, reported convenient usage (P = 0.10). The patients who received ZM syrup had significantly better outcomes (P = 0.036). Conclusions: Herbal compounds, such as ZM mixtures, are acceptably efficacious in cough relief with fewer adverse effects than chemical compounds in the treatment of cold-related cough, especially in infants and younger children.