The oil cakes are by-products of edible oil extraction process from certain industrial plant seeds. They were treated until recently as a low- value agro-waste despite their high protein content. Oil cakes of hempseed and flaxseed contain around 30% proteins, as well as many other bioactive compounds, and as such, they can be processed into a nutritive supplement for animal cell cultivation. The majority of high-value therapeutic proteins today are produced with CHO (Chinese hamster ovary) cells. The use of plant protein hydrolysates as growth media supplements in CHO cell culture has two main purposes: enhancing cell growth and increasing the recombinant protein production. Reactive oxygen species (ROS), represented by hydrogen peroxide, nitric oxide, and free radicals, are regular metabolic products of cells grown in vitro. They affect diverse cellular functions and cause damage of biological macromolecules such as lipids, proteins and nucleic acids. In this work, we investigated the protective effects of flaxseed and hempseed protein hydrolysates (FPH and HPH) obtained by various microbial proteases (Alcalase®, Neutrase®, Protamex®) on hydrogen peroxide-induced oxidative stress in CHO cells producing IgG. Cell cytotoxicity was evaluated through the aspects of cell viability determined by the MTS assay. The results showed that the cell culture supplementation with FPH and HPH, produced by different enzymes, has a mild proliferation effect on CHO cells. When oxidative stress in CHO cells was induced by hydrogen peroxide, FHP obtained by Neutrase® (0.5 g/L), and HPH obtained by Protamex® (2.5 g/L) showed a protective effect. All this indicates benefits of FHP and HPH as cellprotecting agents, but more profound analysis is required to identify molecular species contributing to the observed effects.