Two new Antillean endemic species, Piper abajoense from Puerto Rico, and Piper claseanum from the Dominican Republic, are described and illustrated. The former species resembles the widely distributed Piper hispidum, including the somewhat scabrous leaf surfaces, typically asymmetric leaf bases, and the bracts, flowers, and fruits forming distinct bands around the spike, but is distinguished by the combination of glabrous and stylose fruits (vs. densely puberulent and estylose), laterally (vs. apically) dehiscent anthers, and shorter spikes. The latter species resembles Piper samanense, another endemic species from the Dominican Republic, in vegetative morphology, including the leathery leaves with pellucid dots visible below when dry, but differs in its long-pedicellate flowers and fruits (vs. sessile or pseudopedicellate), puberulent rachis and pedicels (vs. densely white-pubescent), and puberulent vs. pubescent fruits. A phylogeny based on the nuclear ribosomal Internal Transcribed Spacer (ITS) and chloroplast intron psbJ-petA indicates proper placement of these two new species within clades Radula and Enckea, respectively. Two keys are provided, one to all species of Piper from Puerto Rico, the other to the palmate-veined species from the Dominican Republic.