The sea cucumber Holothuria (Halodeima) grisea Selenka, 1867 is distributed from Florida (USA) to southern Brazil. Juveniles of this species are very hardly found in the wild. H. (H.) grisea is very common on sandstone reefs in some localities from the northern coast of Brazil. Because seagrass beds are a conspicuous feature in some of these localities, the authors have speculated that juveniles live in these habitats. Following this species' reproduction period, seagrass beds adjacent to sandstone reefs were inspected in search of juveniles from December to May. Sea cucumbers were found in one of them. Individuals were collected from two areas within the seagrass bed and two areas within neighboring rocky shores, and their contracted body lengths were measured. Mean sizes were significantly smaller in the seagrass areas than in reef areas (post-hoc Tuckey test, P < 0.05). Within the seagrass bed, more than 70% of individuals were smaller than 7.5 cm, whereas 84.9 and 93.3% in the two reef areas were larger than 7.5 cm -the first report of an H. (H.) grisea population dominated by juveniles. Therefore, seagrass meadows should be looked at as possible sources of juveniles for adult populations of H. (H.) grisea in the tropical western Atlantic. Also, given the rarity of juvenile sightings for this species anywhere within its distribution range, the results are very meaningful for future research on its ecology and local and regional fishery management.