Purpose: There is controversy about the effect of the rs1799983 nitric oxide synthase (NOS3) genetic variant on hypertension and blood pressure (BP) levels. The aims of the current study were to examine whether rs1799983 affects BP levels and to identify potential interactions between this polymorphism and other non-genetic risk factors. Methods: A total of 705 subjects were examined for anthropometric and body composition measurements, BP, dietary habits and physical activity. Oral epithelial cells were collected for the identification of rs1799983 using Luminex® 100/200TM System. Results: After adjusted for covariates, TT genotype showed a 2.30-fold higher predisposition of hypertension than GG genotype subjects. According to BP levels, for each risk allele diastolic blood pressure (DBP) increased in 1.99 mmHg. Significant interactions between rs1799983 and saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) were found. Moreover, an interaction with body weight status was observed. Among overweight individuals, T allele carriers showed higher DBP than GG genotype. Conclusion: The present study evidenced that rs1799983 NOS3 polymorphism could be associated with hypertension and DBP among Southern Europeans, being this association influenced by dietary fat (SFA and MUFA) and body mass index.