Various economically important tropical tree species are not well known biologically. We studied the floral and fruit biology of Allariblackia stuhlmannii (Clusiaceae), a dioecious tree species endemic to the Eastern Arc Mountains of Tanzania and Kenya that has become the subject of recent interest by the food industry because of the edible oil that can be extracted from the seeds. We characterised qualitative and quantitative similarities and differences between male and female flowers, the flowering and fruiting phenology, and examined the relationship between fruit crop production and tree size, seeds per fruit, and seed number as a function of fruit mass. There was no significant difference in sugar concentration of nectar between male and female flowers, but male flowers contained significantly more nectar than female flowers. Male trees had larger flowering displays with a tendency for the population to mast profusely between January and March, which coincided with the peak fruiting period. The fruiting period was pronounced from January to March, which appeared to be preceded by a smaller peak in October. Fruit crop was strongly related to tree size, with mean seed number per fruit being 38. Seed quantity per fruit showed a trend to increase with fruit mass, but this relationship was not significant. General physical resemblance of female flowers to male flowers, the latter of which offer multiple floral cues to attract pollinators, suggests a pollination-by-deceit strategy. Our results provide important insights on the natural history of this tree species and carry implications for its future use.