A new octaketide, named cytosporone V (1), and two other known phenylethanoid glycosides (2–3), were isolated from the aerial parts of Pogostemon cablin (Blanco) Benth. The structure of 1 was elucidated by a combination of extensive spectroscopic analyses, including extensive 2D NMR and HR-MS. Compounds 1–3 displayed weak antibacterial activity against two gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus. All isolates were also evaluated for their antiproliferative activities against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15). Compounds 2 and 3 showed significant cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines with IC₅₀ values ranging from 2.73 to 9.52 μM.