The Caribbean basin has suffered alarming numbers of collapsing marine populations due to diseases in recent decades. The well-documented die-off episode of the long-spined sea urchin Diadema antillarum (Philippi, 1845) in the early 1980s, stands out among these collapses. The decline in this keystone species did not just alter the food webs of Caribbean reefs but also modified its community. Nearly 40 years later, Diadema populations have not recovered to pre-die-off density levels. Early in 2022, a new mortality event of D. antillarum has been reported along the Caribbean, including Puerto Rico. Preliminary observations in Culebra revealed that 9 of every 10 individuals were dead or showing disease signs, while no environmental cues associated with these mortalities have been identified. This study aims to characterize the microbiota associated with diseased animals in Puerto Rico.