Transforming growth factor-beta 1 (TGF-β1) is a multifunctional cytokine that plays a pivotal role in airway remodeling observed in the asthmatic airways. C to T base substitution at -509 promoter position in the TGF-β1 gene leads to its increased expression which contributes to airway remodeling in bronchial asthma. We sought to evaluate the association of TGF-β1 -509 C/T promoter variant with clinical asthma and varying degrees of disease severity. Three hundred and eighty-two clinically diagnosed asthma patients and 410 healthy controls were enrolled for the study. Patients were classified into severity classes according to the Global Initiative for Asthma (GINA) guidelines. TGF-β1 -509 C/T genotyping was carried out by amplification refractory mutation system polymerase chain reaction (ARMS-PCR) technique. In the present study, we found significantly higher frequency of TT genotype in asthma patients compared to controls (for TT vs. CC, p = 0.020). In addition, a significant difference was observed in the frequency of C and T allele in patients and controls (for T vs. C, p = 0.029). The heterozygous "CT" genotype was higher in moderate and severe asthmatics compared to mild subset of patients (for mild vs. moderate, p = 0.037). However, there was no significant distribution and association of variant allele with the severity subsets.