Primates are primary seed dispersers for many tropical tree species. Different species of primates vary considerably in ranging and feeding behaviour, seed processing, and in seed defecation patterns. Here we compare the role of two arboreal primate species, howlers (Alouatta palliata), and white-faced monkeys (Cebus capucinus) as seed dispersers in a tropical dry forest in Costa Rica. We found that Cebus produce smaller defecations, spend shorter times feeding per tree, have longer seed dispersal distances, and produce a more scattered pattern of seed deposition in the forest than Alouatta. In addition, Cebus moved more frequently between trees, and consumed fruits of more species than Alouatta. We examined the consequences of the contrasting defecation patterns produced by Cebus and Alouatta on the early seed fate of Acacia collinsii. We found that quantity, but not the identity (Cebus vs. Alouatta) of faecal material affected post-dispersal activity. Seeds in scattered faeces, sufficiently apart from each other (the common defecation pattern of white-faced monkeys), had higher short-term survival than seeds in clumped patterns of faeces (the pattern associated with Alouatta).