Twenty newly born male and female Friesian calves with an average live body weight (LBW) of 30.40±0.36 kg were divided into five similar groups (2 male + 2 female in each group) and continued in a feeding trial until weaning to study the effect of supplementing the algae on suckling calves growth performance. Diet of cows and their suckling calves in G1 did not supplemented with algae and served as a control diet. Whereas, cows and their suckling calves were supplemented with algae and their media at levels of 2 ml (G2) and 4 ml (G3) / kg LBW, as low and high levels, respectively. While, cows in G4 and G5 were unsupplemented with algae, but their suckling calves were supplemented with Chlorella vulgaris algae and their media at the same above levels. Results showed that groups supplemented with high level of algae (G3 and G5) were recorded significantly (P<0.05) the highest digestibility of all nutrients and feeding values followed by groups supplemented with low level of algae (G2 and G4), while control group (G1) had the lowest values. The DMI were the same for different groups, while the intake of TDN and DCP were significantly (P<0.05) higher for G3 and G5 compared to those of control one (G1), but the low levels of algae rations (G2 and G4) were insignificant higher than those of control ration as well. Mostly, blood serum measurements (total protein, globulin and albumin) in addition of creatinine and liver enzymes activity (AST and ALT) were markedly improved versus to those of control group (G1). Moreover, the concentrations of immunoglobulin fractions (IgA, IgM and IgG) were increased significantly (P<0.05) with chlorella supplementation and increased with increasing the level of chlorella supplement. Weaning weight and average daily gain of suckling calves increased significantly (P<0.05) with chlorella algae supplementation as well as with increasing supplementation level. Chlorella supplementation improved significantly (P<0.05) feed conversion, being decreased the amounts of DM, TDN and DCP required per one kg live weight gain. Also, chlorella supplementation improved economic efficiency, which decreased feed cost per one kg live weight gain and increased the total and net revenue of live weight gain and economic efficiency.