The purpose of this study was to investigate and propose possible reference intervals of plasma biochemical analytes in young dogs (< 12 months old) in Japan, using 896 canine plasma samples, collected from an array of veterinary clinics throughout the greater Tokyo metropolis area in Japan. The following biochemical parameters were assessed: albumin (ALB), alanine aminotransferase (ALT), alkaline phosphatase (ALP), amylase, aspartate aminotransferase (AST), blood urea nitrogen (BUN), creatinine (CRE), glucose, lipase, total cholesterol (T-Cho), and total protein (TP) were evaluated. Multivariate linear regression analysis indicated that partitioning according to age or gender may be necessary for some plasma analytes. Age appeared to significantly affect ALB, ALT, ALP, BUN, Glucose, Lipase, and Total Protein (P = < 0.001, < 0.001, < 0.001, 0.013, < 0.001, 0.025, and < 0.001, respectively). On the other hand, gender significantly influenced ALP, Amylase, Lipase, and T-Cho levels (P = 0.017, < 0.001, < 0.001, and < 0.001, respectively) whereas it may be borderline significant with ALT (P = 0.072).