A Research on the biodiversity and distribution of crustaceans in the River Nun estuary, Niger Delta, Nigeria was conducted from November, 2020 to April, 2021. This was done to impliedly monitor certain aspects of the environment, such as eutrophication, pollution warning trends and long-term changes which are signs of human induced environmental disturbance. Crustacean communities seem to be particularly useful for the evaluation of ecosystem status due to the presence of indicator taxa. Water Samples were collected from three sampling stations with collection bottles and taken to the laboratory for analysis. Crustacean samples were collected from four sampling stations. Different sampling techniques were employed in the collection of the crustaceans. Sampling was done with a quadrat of size 0.25m2 at the ebb of the spring tide in each of the stations. Pole seine nets, beach seine nets, visual counts, collections, and burrow counts techniques were also employed. The mean values of physico- chemical parameters ranged from 6.13 to 6.34 for pH, 3.70 to 5.57%o for salinity, 31.07 NTU to 37.92 NTU for turbidity, 3.57mg/L to 3.84mg/L for Total Dissolved Solids (TDS), 3.47mg/L to 3.79mg/L for Total Suspended Solids (TSS), 6.50mg/L to 23.04mg/L for HCO3, 5.66mg/l to 6.33mg/l for Dissolved Oxygen (DO), 0.90mg/L to 1.55mg/L for Total Hydrocarbon Content (THC), 44.41mg/L to 72.07mg/L for Biochemical Oxygen Demand (BOD), 139.70mg/L to 169.45mg/L for Chemical Oxygen Demand (COD), and 0.58mg/L to 1.81mg/L for Total Organic Carbon (TOC) respectively. 27 species of crustaceans belonging to 4 orders, 15 families, and 18 genera were encountered during this study. Among these, the decapods crustaceans were the most abundant, having 24 species out of the 26 species of crustaceans that were identified. Also, the family Graspsidae had the highest numbers of species (7 species), followed by the families Panaeidae (4 species), Portunidae (3 species), and Ocypodae (3 species), respectively. Most of the crustaceans, except Parapenaeus longirotius, Penaeus monodon, and Penaeus satiferus, are usually found either close to or around the fringes of the estuary or around mudflats. The abundance and preponderance of indicator crustaceans such as Decapods, Isopods, and copepods which are known to be negatively correlated to the density of solid waste, which in turn is affected by the presence of human activity reveal an unpolluted environment. It can be concluded that the fishery and environment is not under threat. However, environmental sustainability should be ensured or indeed improved upon.