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Effects of extraction solvent and harvest period on phytochemical analysis and antioxidant and antimicrobial activities of extracts obtained from the freshwater macroalga, Spirogyra sp. were evaluated. The experiment lasted five months, where five crude extracts were obtained by maceration using different solvents: hexane, chloroform, dichloromethane, acetone and methanol. Higher values of yields were recorded in methanolic extracts on February (7.304%) and March (4.812%). All extracts were rich in proanthocyanidins compared to total phenolics and flavonoids. The total amounts of carotenoids were very low (0.060 ± 0001 to 0.171 ± 0.005 mg/g) compared to chlorophylls which were higher in February (6.365 ± 0.075 mg/g) and in March (5.501 ± 0.118 mg/g). The antioxidant activities indicated that the chloroformic and dichloromethanic extracts of February and March exhibited a good activity. The correlation using the Pearson test of phenolic compounds and antioxidant activity tests have confirmed the strong contribution of flavonoids and proanthocyanidins. The greatest antimicrobial activity was found in hexanic extracts at 0.1 to 1 mg/disk. The present findings suggest that Spirogyra sp. can be exploited not only for human health, but also for screening new economic natural antioxidants that could be used in foods, cosmetics and pharmaceutical industries.