This cross-sectional study evaluates the relationship of the dietary inflammatory index (DII), a novel tool developed to measure the inflammatory capacity of a diet, with pulmonary functions and asthma control test (ACT) scores in asthmatic individuals. The study included 120 patients who were diagnosed with asthma for at least one year. The anthropometric measurements, one-day long nutrition uptake records, pulmonary function tests, and ACT scores of the respondents were recorded and compared according to categories of the DII which was calculated from 24- hour recalls. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and ACT scores decreased with increasing DII tertiles (p<0.05). The total energy, carbohydrate, fat, and saturated fat uptake of the participants increased in parallel to DII (p<0.05); while vitamin A, C, and E uptakes, on the other hand, decreased as DII increased (p=0.0001). In conclusion, an increase in the inflammatory potential of diet among asthmatics decreases pulmonary functions and asthma control.