The family Nereididae Blainville, 1818, is one of the most representative group of errant polychaete worms, with about 535 described species in 43 genera, with great biological and ecological importance. The aim of this research was to make a taxonomic analysis of the nereidids associated to red mangrove roots, Rhizophora mangle, in the San Andrés, Old Providence and Santa Catalina Archipelago. This archipelago is part of the Seaflwer Biosphere Reserve. San Andrés is the largest island, having 27 km2 of landmass area, while Old Providence Island, located 95 km to the north of San Andrés, has 17 km2; both islands have well developed mangrove forests, composed mainly by R. mangle. The nereidids, deposited in the Coleccion Estuarina y Marina de la Universidad de Antioquia (CEMUA), were identifid with updated keys, by performing dissections and extracting parts with taxonomic value. Four species of polychaetes from the family Nereididae were found: Neanthes acuminata, Neanthes succinea, Neanthes sp., and Platynereis mucronata. Only N. succinea and N. acuminata had been reported from the Colombian Caribbean, being N. succinea the only species previously reported from the archipielago. In addition, systematic, ecological and biogeographical considerations were added for each species.