Antioxidants in seaweeds have attracted increasing interest for its role in protecting human health. Therefore, the aim of this study was to assess the Total phenolic content (TPC) values and antioxidant activities in red seaweeds Kappaphycus alvarezii and Kappaphycus striatum of different solvent extracts. Total phenolic content (TPC) and antioxidant activities (DPPH scavenging assay and Trolox equivalent antioxidant capacity assay, TEAC) for both K. alvarezii and K. striatum extracts were determined using different solvents at different concentrations (ethanol: 50%, 70%, 100%; acetone: 50%, 70%, 100%; methanol: 50%, 70%, 100%). The TPC value was measured using the Folin-Ciocalteu’s method. The antioxidant activities were measured by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay and Trolox Equivalent Antioxidant Capacity (TEAC) assay. The highest TPC value of K. alvarezii antioxidant extract was obtained by 50% ethanol extracts while for K. striatum obtained by 50% methanol extract. The highest percentage of DPPH free radical inhibition for K. alvarezii was shown by 50% acetone extract while K. striatum was shown using 50% methanol extract. The highest TEAC value for K. alvarezii was shown by 50% acetone while K. striatum extract was shown by 50% ethanol extract. The TPC values and antioxidant activities of all solvent extracts of K. striatum were significantly higher (p< 0.05) than K. alvarezii antioxidant extracts. The TPC values showed strong correlation (r = 0.797) with TEAC values for K. alvarezii antioxidant extract (p< 0.01). The TEAC values also showed strong correlation (r = 0.735) with percentage of DPPH free radical inhibition for K. alvarezii (p< 0.01). The TPC value, DPPH free radical scavenging assay and TEAC assay for K. striatum extracts showed strong correlation (r> 0.8) with each other (p< 0.01). In summary, K. striatum showed better antioxidant activity and higher TPC value than K. alvarezii.