Studies on the constituents of the unripe fruits of Siraitia grosvenori led to the isolation of three new cucurbitane triterpene glycosides, 11-oxomogroside III (10), 11-dehydroxymogroside III (11), and 11-oxomogroside IV A (12). Their structures were determined on the basis of detailed analyses of 1D, 2D-NMR spectroscopic methods. All of the compounds isolated from the unripe fruits of S. grosvenori were tested for cytotoxic activities against tumor cells, HCT-116 and SMMC-7721.