The EtOAc, n-BuOH and H2O subextracts of the crude MeOH extract of the aerial parts of Sedum caespitosum (cav.) Dc. were screened for cytotoxicity using the neutral red assay in Chinese hamster ovary cells as well as their protective effect against H2O2 induced cytotoxicity in human red blood cells. While the extracts did not show cytotoxicity, they displayed a protective effect compared to a blank and ascorbic acid. Gallic acid (1), kaempferol 3-O-alpha-rhamnopyranoside (2), quercetin 3-O-beta-glucopyranoside (3), quercetin 3-O-alpha-rhamnopyranoside (4) and myricetin 3-O-alpha-rhamnopyranoside (5) were isolated from the EtOAc extract and identified by 1D- and 2D-NMR. The protective effects of the isolated compounds against H2O2 induced cytotoxicity in human red blood cells were evaluated and 5 was the most active.