Aim of this study was to investigate the effect of flaxseed oil supplementation on the digestion, immunoglobulin concentration, some blood parameters, average daily gain, feed conversion and economic efficiency of suckling Friesian calves. A total of 28 newly born Friesian calves with weighing 31.42±1.9 kg were divided into two similar groups, 14 calves in each group. The first group (G1) was served as a control, while the second group (G2) was supplemented with 0.2 ml/kg LBW from flaxseed oil in suckling milk from birth up to weaning. Results showed that digestibility coefficients of DM, OM, CP, CF, EE and NFE and feeding  values as TDN and DCP as well as feed intakes as TDN and DCP were higher (P<0.05) in G2 than in G1. Blood plasma immunoglobulins concentrations were higher (P<0.05) during different suckling intervalsin G2 than in G1. Red and white blood cells count, percentages of monocytes, neutrophils and package cell volume, and haemoglobin concentration increased (P<0.01) in G2 than in G1. Percentages of basophils, eosinophils and lymphocytes were not affected by supplementation. Concentration of total protein, albumin and globulin in plasma were increased (P<0.05-P<0.01), while, albumin to globulin ratio and concentration of total lipids, creatinine and urea-N concentrations decreased (P<0.01) in G2 than in G1. Plasma glucose concentrations and AST and ALT activities were nearly similar in both groups. Live body weight, average daily gain and feed conversion improved (P<0.001) in G2 than in G1. Economic efficiency was higher (P<0.05) in G2 than in G1. It could be concluded that flaxseed oil supplementation in milk of suckling Friesian calves (0.2 ml/kg LBW) during the suckling period improved growth performance and economic efficiencies as well as immune-response of Friesian calves without adversity effects on digestibility, haematological and biochemical parameters.