Seven species of helminths and six species of arthropods are reported from 23 of 40 brown pelicans, Pelecanus occidentalis, collected from various localities in Puerto Rico. Helminth parasites include three nematodes (Contracaecum multipapillatum, Contracaecum mexicanum, and Eustrongylides sp.), three trematodes (Galactosomum darbyi, Mesostephanus appendiculatoides, and Ribeiroia ondatrae), and one cestode (Tetrabothrium sulae). Arthropod parasites include Colpocephalum occidentalis, Neottialges apunctatus, Ornithodoros capensis, Phalacrodectus pelecani, Phalacrodectus punctatissimus, and Phalacrodectus sp. The presence of R. ondatrae in the brown pelican is a new species host record, and P. pelecani, P. punctatissimus and N. apunctatus are new subspecies host records. C. multipapillatum, C. mexicanum, G. darbyi and M. appendiculatoides are new locality records for Puerto Rico, and N. apunctatus, P. pelecani, P. punctatissimus and T. sulae are new locality records for the Caribbean. Necrosis produced by C. multipapillatum, C. mexicanum, and R. ondatrae may have contributed to the emaciation and death of the brown pelicans examined in the present study.