Abstract: Two species of marine algae, Gracilaria edulis and Enteromorpha lingulata, from Chennai coast were evaluated for their antioxidant and antiproliferative activities. Both algae were extracted with three solvents: methanol (M), chloroform (C) and ethyl acetate (E). The M, C, E extracts were investigated for 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging, Beta-carotene Bleaching (BCB), total reducing (TRA) and Growth Inhibitory (GI) activities and Total Phenolic Content (TPC). Thin Layer Chromatography (TLC) was used for qualitatively compare DPPH radical-scavenging activity. Except for BCB, E. lingulata extracts showed comparable (TRA) or higher (DPPH radical-scavenging) antioxidant activity, TPC and GI in HCT15 cells than the extracts of G. edulis. E and C extracts of E. lingulata showed greater antioxidant and GI activities in HCT15 cell (no GI in A549) than M extract. Although M extract of G. edulis showed slightly greater DPPH radical-scavenging activity than C and E extracts, M showed lower TRA, TPC, BCB and GI in HCT15 cells than E and C extracts. None of the extracts showed GI in A549 cells but the GI trend in HCT15 cells mirrored the one seen for all extracts of both algae for TPC (E>C>M; E. lingulata>G. edulis). Except for the E extract of G. edulis which showed slight pro-oxidant activity in the BCB assay, its C and M extracts showed greater BCB inhibition than all the E. lingulata extracts. For all extracts of both algae, DPPH radical-scavenging activity in TLC was associated with the more polar compounds in the extracts.