This research aimed at screening in vivo antioxidant and anti-inflammatory activities as well as in vitro antimicrobial and cytotoxic activities in Codium tomentosum, Ulva lactuca and Hypnea musciformis, collected form the Suez Canal, Egypt. Samples were cleaned from epiphytes, washed, air dried and powdered. All the methanol/methylene chloride crude extracts showed a marked antioxidant effect compared to the reference drug vitamin E on alloxan induced diabetic rats and Hypnea musciformis (red algae) was the most potent (60.18%). Also, it showed the maximum anti-inflammatory activity in carrageenan-induced rat paw edema. Both extracts of H. musciformis and U. lactuca showed a wide spectrum antibacterial activity, and the highest activity appeared against Klebsiella pneumoniae (clinical culture). Moreover, all the crude extracts showed a promising cytotoxic activity (> 70%) against liver (HEPG2) and prostrate (PC3) cancer cell lines using Sulpho-Rhodamine-B (SRB) assay. The ethyl acetate fractions of U. lactuca, C. tomentosum and H. musciformis were significantly enhanced in HEPG2 with IC50 (12.8, 24.5 and 17.8 μg/ml), respectively, compared to the control doxorubicin. Such biological activities might be attributed to the presence of phenols, flavonoids, and tannins, as active constituents in all algal extracts. Besides Alkaloids observed in U. lactuca and H. musciformis, as well as saponins from U. lactuca.