Brain natriuretic peptide (BNP/NPPB) is a member of the natriuretic family involved in the regulation of blood pressure and blood volume as well as lipolysis control in human fat cells. Thus BNP may play a role in energy metabolism and metabolic diseases. We therefore assessed the association between the BNP promoter T-381C polymorphism and risk of type 2 diabetes and metabolic and BNP expression traits in several population samples. In French population-based samples ( n = 3216), we found that individuals bearing the -381CC genotype had lower ( P = 0.005) fasting glucose levels than -381TC or -381TT individuals. Moreover, the -381CC genotype was less frequent in individuals with type 2 diabetes ( n = 280, 13.6%) or with impaired fasting glucose ( n = 248, 12.9%) compared with normoglycaemic individuals ( n = 2485, 17.8%). The adjusted odds ratio (OR) (95% CI) of type 2 diabetes for -381CC individuals was 0.69 (0.47–1.00), P = 0.05, when compared with -381T allele bearers. We replicated this association in four additional case–control studies for type 2 diabetes. The overall OR (95% CI) of type 2 diabetes was 0.85 (0.76–0.96), P = 0.008, (under a recessive model) (3593 cases and 6646 controls in total). We also found that the -381C allele was associated with higher plasma BNP concentrations ( P = 0.015, n = 634) and higher BNP promoter activity in reporter gene assays. Collectively, these data suggest that relatively high BNP expression may protect against type 2 diabetes in humans.