A new platyrrhine, Miocallicebus villaviejai gen. et sp. nov., from the middle Miocene of La Venta (Colombia) is described. The specimen consists of a right maxillary fragment preserving a root of M1, a complete M2, and a fragmentary M3. Miocallicebus is included in the Callicebinae on the basis of M2 structure, but it differs from extant Callicebus in its much larger size and the position of the pterygoid process. Morphological analysis of M2 structure suggests that the Callicebinae are more closely related to the pitheciinae than to other platyrrhine taxa, supporting the phylogenetic reconstruction proposed by recent molecular biological studies. The Callicebus-lineage is likely to have appeared by the middle Miocene age in the La Venta fauna.