A new species, Botryocladia caraibica sp. nov., is described from the Caribbean Sea on the basis of comparative morphology and rbcL sequence analysis. The new species is often confused with and reported in the literature as B. pyriformis (Børgesen) Kylin. In B. pyriformis a section of the solid stipe shows an abrupt transition between the cortex and medulla, and the vesicle wall is composed of two cell-layers with irregular and almost complete cortication; in B. caraibica the transition between cortex and medulla is more gradual, and the vesicle wall is 3-5 cell-layered with complete cortication. Reproductive structures in B. caraibica are unknown. Tetrasporangia of B. pyriformis are newly documented.