Seven new polyhydroxylated oleanane-type triterpene saponins, arenarosides A-G (<b>1</b>-<b>7</b>), together with four known compounds, were isolated from an ethanol extract of the aerial parts of the Vietnamese plant <i>Polycarpaea arenaria</i>. The chemical structures of the newly isolated oleanane saponins were elucidated on the basis of spectroscopic and spectrometric analysis, especially 2D NMR and HRMS. Biological evaluation revealed that <b>3</b>, <b>4</b>, <b>6</b>, and <b>7</b> showed moderate activities against four human cancer cell lines (A549, HTC116, PC3, and RT112) with IC<sub>50</sub> values of 6.0-9.9 μM, and <b>3</b>, <b>4</b>, <b>5</b>, and <b>7</b> also displayed promising antiangiogenesis effects with IC<sub>50</sub> values <5 μM in the test system used. Among the isolates, arenaroside D (<b>4</b>) exhibited the most potent inhibitory effects, not only in cancer cell proliferation but also in angiogenic activities. Preliminary SAR studies revealed that the presence of an acetyl group at C-22 in oleanane-type triterpene saponins increases these bioactivities.