Asthma and obesity are both a major public health problems affecting large numbers of individuals across the globe. Link between obesity and asthma is now considered as a recognized fact, and many epidemiological studies, found that overweight and obese people had a higher chance of developing asthma, with more severe symptoms. Assessment of the relationship between body mass index and asthma control. A cross-sectional study, that included 100 patients diagnosed with asthma, attending the respiratory disease consultatory unit at Baghdad teaching hospital. Body mass index was calculated by (BMI= weight in Kg/Height in m2), and Asthma control was assessed using asthma control test questionnaire forma. Statistical analysis done using, Test of normality, Kruskal Wallis test and Chi square analysis. Only 10% of the studied patients had controlled asthma, while most of the patients (90had uncontrolled asthma, of those 24% have normal body mass index, 30% are overweight, and 36% are obese. There is a significant increase in asthma control test levels as body mass index decrease (P value <0.05). A significant inverse relationship between body mass index and asthma control.