Red seaweeds were investigated, using SCUBA, from waters around the island of Cozumel off the east coast of the Yucatan Peninsula in Mexico. One hundred and eighteen species of Rhodophyta were collected and identified. Forty-five of these are reported for the first time from Cozumel, and of these 11 are new records for Mexico. There was a distinct change in the deep water flora between wet and dry seasons; the dry season had more species with northern ranges in comparison with the flora in general. The wet season had few north-ranging species. Fifty-four epiphytic or hemiparasitic species were identified, most frequently on Halimeda tuna, Dictyota cervicornis and Sargassum spp. This account brings the total macroalgal taxa reported from Cozumel to 385, the richest flora of any locality in the Caribbean region of Mexico.