Helicobacter pylori infection, which is a common cause of atrophic gastritis, has been reported to represent a causal factor increasing the vascular damage and consequent albuminuria. On the other hand, decreased serum pepsinogen (PG) I/II ratio can be used to assess gastric mucosal atrophy. To the best of our knowledge, there are no studies investigating the correlation between PG I/II ratio and diabetic nephropathy. Therefore, we investigated a relationship between PG I/II ratio and degree of urinary albumin excretion (UAE) in patients with type 2 diabetes. We evaluated relationships between PG I/II ratio and degree of UAE or estimated glomerular filtration rate as well as various factors, including age, body mass index, blood pressure, hemoglobin A1c, serum lipid concentrations, uric acid or C-reactive protein in 333 consecutive patients with type 2 diabetes. PG I/II ratio correlated positively with logarithm of UAE in all patients (r = 0.174, P = 0.0016) and in patients without Helicobacter pylori infection (r = 0.352, P < 0.0001). Multiple regression analysis identified that PG I/II ratio correlated independently with logarithm of UAE in all patients (β = 0.264, P = 0.0005) and in patients without Helicobacter pylori infection (β = 0.295, P = 0.0022). These data suggest that serum PG I/II ratio is correlated with diabetic nephropathy.