Merauke Regency is located in the southern part of Papua, directly adjacent to Papua New Guinea. It has a mangrove ecosystem that is still good (pristine) which is quite extensive and rich in molluscs and crustaceans which are key fauna in the mangrove ecosystem. The aims of this research were to know the structure of molluscs and crustaceans community in mangrove ecosystem in this area. A study was conducted in October 2019 in 13 stations. Molluscs and crustaceans sample were collected in each location using a plot measuring 10 x 10 m. Samples were taken for 20 minutes by the same two people in each plot at low tide. From this study found 11 species of the crustaceans and 6 species of the molluscs. Cerithidea obtusa, Littoraria scabra and Cassidula angulifera of the molluscs group were macrobenthos that had a relatively wide distribution. The highest abundance was found in MRKM22 station (5.67 individuals/m2) and the lowest was in MRKM33 (0.25 individuals/m2). The molluscs and crustaceans found in this study were common species in mangrove ecosystem. The value of species diversity index (H') ranged from 0.63 to 1.56. This value indicated the diversity of molluscs and crustaceans species was of low-moderate condition. Evenness index (J') ranged from 0.56 to 0.99 and dominance index (C) ranged from 0.24 to 0.56. In general, these ecological values showed that the molluscs and crustaceans community in each station is in a relatively stable condition.Kabupaten Merauke terletak paling selatan dari Papua yang berbatasan langsung dengan Papua Nugini, serta memiliki ekosistem mangrove yang masih baik (murni), cukup luas dan kaya akan moluska dan krustasea, yang merupakan fauna kunci dalam ekosistem mangrove. Penelitian ini bertujuan untuk mengetahui struktur komunitas moluska dan krustasea pada ekosistem mangrove. Penelitian dilakukan pada bulan Oktober 2019, di 13 stasiun. Pengumpulan sampel makrobentos di tiap lokasi menggunakan plot berukuran 10 x 10 m. Sampel diambil selama 20 menit oleh 2 orang yang sama di setiap plot, saat air surut. Dari penelitian ini ditemukan 11 jenis krustasea dan 6 jenis moluska. Cerithidea obtusa, Littoraria scabra dan Cassidula angulifera dari kelompok moluska memiliki penyebaran relatif luas. Kepadatan tertinggi terdapat di stasiun MRKM22 (5,67 individu/m2) dan yang terendah di stasiun MRKM33 (0,25 individu/m2). Moluska dan krustasea yang ditemukan dalam penelitian ini merupakan jenis-jenis yang umum hidup pada ekosistem mangrove. Nilai indeks keanekaragaman jenis (H’) berkisar 0,63–1,56. Nilai ini menunjukkan keanekaragaman jenis baik moluska maupun krustasea dalam kondisi rendah–sedang. Indeks kemerataan jenis (J’) berkisar 0,56–0,99 dan nilai indeks dominasi jenis (C) berkisar 0,24–0,56. Secara umum, nilai-nilai ekologis ini menunjukkan komunitas moluska dan krustasea di setiap stasiun penelitian berada dalam kondisi yang relatif stabil
