After pollination, the spathe tube becomes tightly reclosed and rots off, taking with it the remaining staminate flowers. Generally the dehiscence of the spathe tube follows a smooth line of thickened, often raised tissue, which is not readily apparent when the spathe first opens but which may become conspicuous by the time the spathe is closing. Part of the staminate spadix, generally including all of the sterile staminate flowers, is closed into the spathe tube. This material eventually rots but remains within the spathe tube. As in the case of Alocasia pubera (van der Pijl, 1933), the staminate flowers of Syngonium may be good places for insects to oviposit since part of the staminate spadix remains enclosed in the spathe tube and would provide an ideal hatching ground for larvae.

At maturity of the syncarpous fruit, the spathe tube is usually colored on the exterior, even though it is usually green at the time of flowering. The spathe tube usually also opens to expose the syncarp. The syncarp is generally pale, with brown flecks representing the original epidermal tissue. Sometimes the spathe tube breaks up and turns inside out, with its bright, colorful interior exposed against the white syncarp, e.g., S. triphyllum. Birdsey (1955) reported that only two species, namely S. 'wendlandii and S. mauroanum, had syncarps that matured white, but 1 found this to be true also for S. triphyllum. In such cases the fruits might be adapted for bird dispersal, since they would be highly visible and could be pecked open by birds. In most cases, however, the fruits seem better suited for mammal dispersal (presumably monkeys) because they are not very colorful, yet they are fragrant.

Each fruit of Syngonium contains 50-100 or more seeds. These are generally somewhat ovoid or cylindroid, usually 5-10 mm long and 3-6 mm in diameter, with both ends rounded. The pericarp is usually brown or black with the whole interior white and moderately soft. Germination of the fruits is prompt and viability of the seed is lost promptly if they are allowed to dry out.