The taxonomy of Peperomia (Piperaceae) in Taiwan is reconsidered. In the present study, six taxa are recognized, based on detailed morphological observations and ITS sequences derived from fresh material obtained from living plants. Details of the characters are discussed, including the morphology of the leaf epidermis and pollen grains. Synonyms are treated. Descriptions of the species, phenology and a key to Peperomia in Taiwan is also provided.