In the present study the production of phenolic acids and flavonoid compounds by E. gracilis exposed to two cadmium concentrations (0.02 and 0.14 mM) was evaluated using high-performance liquid chromatography (HPLC). The results showed that E. gracilis exposed to 0.02 mM Cd+2 increased significantly the total content of phenolic compounds (798.46 ± 12.61 μg GA/g) and total flavonoids (241.34 ± 47.63 μg QE/g) with respect to the control (137.34 ± 19.80 μg QE/g DW and 549.00 ± 8.57 μg GA/g DW, respectively). However, no significant increase in the total content of phenolic compounds (568.54 ± 17.42 μg GA/g DW) and total flavonoids (141.11 ± 9.36 μg QE/g DW) were observed in E. gracilis exposed to 0.14 mM Cd+2. Further research is necessary to determine the specific role of flavonoids in E. gracilis exposed to high concentrations of Cd+2.