Sea cucumbers are marine animals of the Holothuroidea Class that have ecological, health, and socioeconomic benefits. This study aims to determine the structure of the sea cucumber community on Harapan Island and East Penjaliran Island, Kepulauan Seribu National Park, Kepulauan Seribu Regency. Data collection was conducted in January 2020, where each island was divided into two stations, and each station was divided into three substations for data retrieval. The method is a quadratic transect method using a plot measuring 1x1 m. In each square plot, observations were made regarding the type and number of sea cucumbers found and water quality parameters, including salinity, temperature, pH, DO, and total organic matter. Observation parameters include diversity index, uniformity index, frequency, density, important value index, dominance, and sea cucumber distribution index. During the study, species found on Harapan Island include H. atra, H. scabra, H. leucospilota, Bohadschia marmorata, and Stichopus herrmanni. Meanwhile, species found on East Penjaliran Island include H. atra, H. leucospilota, H. coluber, H. pardalis, H. fuscocinerea, H. hilla, Bohadschia marmorata, Stichopus ocellatus, and Stichopus monotuberculatus. The most abundant and predominant species on both islands is Holothuria atra. The average diversity index on Harapan Island falls into the low category, while East Penjaliran Island is classified as medium. The dominance index of both islands is low and has a uniform distribution. Environmental conditions and sea cucumber exploitation affect the structure of sea cucumber communities on both islands.