Recent years have witnessed great interest in using γ-irradiation to stimulate biological processes in microalgae to increase their productivity and the naturally effective ingredients. The findings demonstrated that the algae species had high-quality phytochemicals, which may either directly or indirectly support and maintain the health of living organisms. The purpose of this study was to assess the growth and some biochemical aspects of some microalgae, including Spirulina platensis, Chlorella vulgaris,and Scenedesmus obliquus. These microalgae were irradiated with differ­ent doses of gamma irradiation (0.0, 100, 200, 300, 400, 500, 600, 700, 800, 900, and 1000 Gray). The optimum doses of gamma irradiation that significantly increased the maximum growth value and biomass productivity after two weeks in A. platensis, S. obliquus, and C. vulgaris were 700, 300, and 200 Gray (Gy), respectively, in contrast to the control group. The growth value and biomass productivity declined above the optimum dose. The biomass yield and growth rate decreased drastically upon exposure of cultures to a dose of 1000Gy. Gamma irradiation treatments in the three algae significantly increased the biochemical contents of malondialdehyde, free proline, nitric oxide, and total soluble protein, as compared to the untreated algae (control). The obtained data revealed high values in S. obliquus at 300Gy, followed by A. platensis at 700Gy,and C. vulgaris at 200Gy, respectively, as compared to the control. Therefore, treatments of A. platensis, S. obliquus,and C. vulgaris with the optimum dose of γ-irradiation significantly increased the growth rates and biomass yield of the three algae, which is of great importance in increasing income. It also increases the total content of proteins (natural, safe, cheap, available, and easy to obtain) that are important and beneficial to human and animal health for future applications, especially in countries that suffer from malnutrition.