Different feeding habits may affect the blood parameters in fish species of the same family, even if they live in the same marine habitat. The aim of this study was to compare some haematological and biochemical parameters of two marine fish species of the same family, the saupe Sarpa salpa (Linnaeus, 1758) and the common two-banded seabream Diplodus vulgaris (Geoffroy Saint-Hilaire, 1817), and to establish the similarities and differences between these species. For this purpose red blood cells (RBC), haemoglobin concentration (Hb), haematocrit (Hct), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), glucose (GLU), triglycerides (TRIG), cholesterol (CHOL), serum total protein (TP), albumin (ALB), globulins (GLO), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were determined for 30 fish from each species. Statistical analysis showed significant differences in some haematological and biochemical (RBC, Hb, Hct, TP, ALB, GLO, AST, ALT, ALP and LDH) parameters between the two species. Lower values of RBC, Hb and Hct were found in S. salpa in comparison with D. vulgaris. These differences could be attributed to the feeding behavior, life style and habitat adaptation of the different fish species of the same family and contribute to knowledge of reference values of blood parameters in Sarpa salpa and Diplodus vulgaris. No significant differences were found in MCV, MCH, MCHC and GLU, TRIG, CHOL.