The phytochemical composition of passionfruit juice (PFJ) was hypothesized to have valuable anti-cancer activity, and this was tested in a BALB/c 3T3 neoplastic transformation model. A higher concentration of PFJ compared with a lower concentration was effective in reducing the number, size, and invasiveness of transformed foci. When incubated with another mammalian cell line, the MOLT-4, PFJ was unable to alter the cell cycle kinetics while at the same time was successful in inducing the activity of caspase-3, an enzyme that commits the cell to apoptosis. This suggests that phytochemicals found in PFJ were able to produce the changes in transformed foci due to apoptotic mechanisms rather than by a reduction in cell proliferation. These beneficial results were achieved at levels that could theoretically be attained in the plasma after consumption of the juice.