Two new xanthone derivatives, pestalotiones A (1) and B (2), one new diphenyl ketone riboside, pestalotione C (7), and one new diphenyl ether, pestalotione D (8), along with five known compounds isosulochrin dehydrate (3), 3,8-dihydroxy-6-methyl-9-oxo-9H-xanthene-1-carboxylate (4), isosulochrin (5), chloroisosulochrin (6), and pestalotether D (9), were isolated from the crude extract of the plant endophytic fungus Pestalotiopsis theae (N635). The structures of the new compounds were unambiguously deduced by HRESIMS and 1D/2D-NMR spectroscopic data. Compound 6 showed modest cytotoxicity against the HeLa cell line with an IC₅₀ value of 35.2 μM. Compound 9 also showed cytotoxic to the HeLa and MCF-7 cell lines, with IC₅₀ values of 60.8 and 22.6 μM, respectively. Additionally, compounds 1 and 2 exhibited antioxidant activity in scavenging DPPH radical with IC₅₀ values of 54.2 and 59.2 μg/mL, respectively.