The effect of CO₂ enrichment on the content of minerals, crude proteins, carbohydrate, and total polyphenols and flavonoids as well as antioxidant, cytotoxic and antibacterial activity of Arthrospira platensis were studied. A. platensis grown with CO₂ enriched medium had less crude protein but more carbohydrate and phytochemical compounds. Increased calcium and iron contents were also obtained. CO₂ seemed to increase polyphenols, flavonoids and tannins, which in turn increased antioxidant activities using the DPPH assay (IC₅₀ = 1.64 μg mL^-1). Moreover, CO₂ enrichment increased antibacterial activity, namely against E. coli and S. enterica. Cytotoxicity was increased with CO₂, especially with the OVCAR (IC₅₀ = 17.5 μg mL^-1) and MCF-7 (IC₅₀ = 14.5 μg mL^-1) cell lines. GC-MS analysis showed that in CO₂ free medium 12 bioactive compounds were found. The most abundant compounds were hexadecanoic acid, methyl ester and n-hexadecanoic acid. However in CO₂ enriched medium results showed the presence of only 7 compounds. Therefore, the use of CO₂ in the production of algae may have a positive environmental benefit to reduce the carbon pollution from the atmosphere and provide a better Spirulina production and quality.