Brachionus plicatilis is a rotifer that considered an important live feed in aquaculture for feeding the initial stages of many fish larvae. This study aimed to determine the growth, survival rate and biochemical alterations of Dicentrarchus labrax (sea bass) larvae fed on B. plicatilis treated with sublethal concentrations of cadmium chloride (CdCl₂) and copper sulphate (CuSO₄). This study is extended to evaluate the alteration in the nutritional value of B. plicatilis upon the exposure to sublethal doses of these heavy metals. The results showed that the   total length and width means of D. labrax larvae reared on B. plicatilis exposed to CuSO₄ and CdCl₂ increased significantly when compared to their control (p< 0.05.). D. labrax larvae fed on rotifers treated with CuSO₄ and CdCl₂showed a significant decrease in their survival percentages (p < 0.001) and their total lipids and protein levels (p < 0.001) when compared to their control. Moreover, the level of carbohydrate and lipid decreased significantly (p < 0.05) in the B. plicatilis exposed to sublethal concentration of CdCl₂ and CuSO₄. Most of the essential and nonessential amino acids in B. plicatilis exposed to these heavy metals were partially decreased while methionine, phenylalanine, histidine and leucine showed significant increase. Treating B. plicatilis with CdCl₂ showed a significant decrease in mono and poly unsaturated fatty acids. The oleic acid ((C20:1 ω9) and the caprylic acid (C8:0) decreased in B. plicatilis exposed to CdCl₂ and CuSO_4, while the Eicosatrienoic acid (C 20:3ω3) and the Eicosapentaenoic acid (C 20:5ω3) were not detected. The Arachidonic acid (C20:4 ω6) decreased significantly in treated B. plicatilis with CdCl₂.  The present work concluded that, D. labrax larvae feeds on B. plicatilis exposed to sublethal concentration of Cd and Cu heavy metals showed marked effect on the survival rate and biochemical composition.