Asthma is an inflammatory disease, which causes airflow limitation and increase insulin resistance. The present study was carried out in order to investigate insulin resistance and the effect of inhaled corticosteroid (ICS) on insulin sensitivity in asthmatic patients. A registered (IRCT201605247411N2) interventional, quasi-experimental trial was performed from 2014 to 2015 in Imam Khomeini hospital Ahvaz, Iran. Patients with mild to moderate asthma participated in this study. Spirometry, fasting blood sugar (FBS), blood sugar 2 hour post prandial (BS2HPP), HbA1C, low density lipoprotein (LDL), high density lipoprotein (HDL), Insulin Level, and C reactive protein (CRP) were measured. Then Homeostatic Model Assessment-Insulin Resistance [HOMA-IR] Index calculated. Data were analyzed using paired t-test and McNemar’s test using SPSS 20.0 Software. The study consisted of 35 non-diabetic patients suffering from asthma (20 men and 15 women) with a mean age of 36.6 ±12.3 years. Inhaled corticosteroid had a significant effect on spirometric parameters, but it had no significant effect on other variables. At baseline, mean HbA1C, insulin level and HOMA-IR were 5.5%, 10.9 mIU/L and 2.7 respectively. None of these values changed significantly after treatment with inhaled corticosteroid for two months. The results indicated that there is no relationship between ICS and increased insulin resistance in asthmatic patients.