The Dysoxylum genus that belongs to the Meliaceae family is widely distributed from India and Sri Lanka throughout Malaysia and Indonesia to Australia and New Zealand. Numerous types of compounds have been reported, including sesquiterpenoids, limonoids, triterpenoids, and alkaloids. One of the members of this genus is Dysoxylum alliaceum. Reports on the phytochemical constituents of this species are limited. During our search for naturally occurring tropical plant compounds with intriguing structures and biological properties, the stembark of D. alliaceum, which showed cytotoxic activity against MCF-7, A549 and CV-1 cell lines, was investigated. This paper also describes the chemical structure of the isolated compounds using HR-ESI-MS, FTIR, and NMR. As a result, eight triterpenoid compounds belonging to tirucallane-type (1-8) were identified, including cneorin-NP36 (1) toonapubesin A (2), toonapubesin B (3), chisopanin M (4), 21 α-methylmelianodiol (5), 21 β-methylmelianodiol (6), hispidone (7), and odoratone (8). These compounds are newly discovered in this plant. Furthermore, toonapubesin A (2) showed the highest selectivity against A549 cancer cell lines with IC50 value of 7.81±0.02 μM, resulting in no activity towards CV-1 cells. The current result could indicate that this plant produces potential natural product compounds with anticancer properties.