Silymarin and phenolic compounds have great pharmaceutical applications, particularly as hepatoprotective agents. Silymarin content in Silybum marianum wild populations is low with significant differences between the individuals and the areas of these populations decreased due to the increasing interest in the plant. Therefore, cell suspension culture technique is an alternative and sustainable procedure for the bioproduction and conservation of the plant. The aim of the present study was the production of silymarin and certain phenolic compounds from Silybum marianum cell suspension cultures by the supplementation of the precursor amino acid; L-phenylalanine. Seeds were collected from wild plants at Alexandria desert road and germinated in vitro. Seedlings root segments were cultured on Murashige and Skoog medium supplemented with 4.55 μM 2,4-dichlorophenoxy acetic acid and 4.44 μM 6-benzyladenine for the induction and proliferation of callus. Cell suspension cultures were established in the same medium supplemented with L-phenylalanine at different concentrations (302.68, 605.36 and 908.05 μM). L-Phenylalanine elevated the cells biomass and the accumulation of silymarin and some phenolic compounds. The significantly highest silymarin accumulation reached 66.33% increase compared to the control. This study highlights the potential of L-phenylalanine for the in vitro production of silymarin-rich extracts and protecting the environment by preventing the overcollection of the plant.