Six compounds were isolated from the n-BuOH fraction of the aerial parts of Aruncus dioicus var. kamtschaticus including: sambunigrin (1), prunasin (2), aruncide A (3), aruncide C (4), 1-O-caffeoyl-${eta}$-D-glucopyranose (5), and caffeic acid (6). Their structures were confirmed by comparing the spectral data with those reported in the literature. The isolated compounds (1 - 6) were then examined for their cytotoxic effects towards MCF-7, HL-60, and HeLa cancer cell lines, as well as their DPPH radical scavenging activity. The results indicated that compound 4 possessed the strongest inhibitory effect toward HeLa cell line with $IC_{50}$ value of $5.38{pm}0.92{mu}M$. Compound 3 possessed selective cytotoxic activity on HL-60 cells with $IC_{50}$ value of $6.27{pm}0.17{mu}M$, compound 5 was found as the best in inhibiting proliferation with $IC_{50}$ value of $2.25{pm}0.09{mu}M$, and the other compounds showed significant inhibition with $IC_{50}$ values ranging from 6.10 to $11.27{mu}M$. Compound 5 also displayed the strongest cytotoxic effect toward MCF-7 cell line ($IC_{50}$ $4.32{pm}0.15{mu}M$). Both 5 and 6 demonstrated strong radical scavenging activity ($IC_{50}$ $6.87{pm}0.03$ and $4.33{pm}0.22{mu}M$, respectively). Compounds 1 and 5 were isolated for the first time from this plant.