Eucalyptals A-C (1-3) with a new skeleton of 3,5-diformyl-isopentyl phloroglucinol-coupled cadinane were isolated from the fruits of Eucalyptus globulus. Their structures were elucidated by spectroscopic analysis, and that of 1 was confirmed by single-crystal X-ray diffraction. The biosynthetic pathway of 1-3 was also postulated. Compounds 1-3 exhibited selective cytotoxicity against the HL-60 cell line.