A phytochemical study on an ethanol extract of Ardisia arborescens resulted in the isolation of five new diarylundecanones, named ardisinones A-E (1-5). The structures were established by HRESIMS and NMR ((1)H, (13)C, DEPT, HSQC, HMBC) as 11-(2-acetoxy-6-hydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)undecan-1-one (1), 11-(2-acetoxy-6-hydroxyphenyl)-1-(2,6-dihydroxy-4-methoxyphenyl)undecan-1-one (2), 1-(2,6-dihydroxy-4-methoxyphenyl)-11-(2,6-dihydroxyphenyl)undecan-1-one (3), 1-(2,4,6-trihydroxyphenyl)-11-(2,6-dihydroxyphenyl)undecan-1-one (4), and 1-(2,4,6-trihydroxyphenyl)-11-(2-hydroxyphenyl)undecan-1-one (5). In our in vitro disk diffusion assay, compounds 1 and 4 showed some slight inhibition of three bacteria, while 2 and 3 did not show antimicrobial activity.