One of the recently considered pollutants is microplastic particles. To investigate this contaminant, 15 samples of sediment were sampled from Khor-e-Musa estuary. Samples were transferred to the laboratory in thick plastic bags for extraction and counting of microplastic particles. H2O2 was first used to remove organic matter in the samples. Then, using the condensation separation method, the microplastic particles were separated from the sediment particles and finally identified and counted by using binocular optical microscopy. The average concentration of microplastic particles in the study area was 11.67 per 250 g of sediment and the maximum and minimum concentrations were 22 and 1, respectively. In this study, about 49% of the found microplastics were stringed, 36% multifaceted, and 14% spherical. The predominant color of these particles was white/transparent and black/gray, which accounted for 32% and 36% of the total microplastics, respectively. Also, about 13, 14, and 5 percent of the microplastics were yellow/orange, red/pink, and blue/green, respectively. In general, about 52, 33, 8, 3, and 3% of microplastics are related to microplastic particles with sizes less than 100, from 100 to 250, from 250 to 500, from 500 to 1000, and from 1000 to 1000, respectively. It was 5,000 micrometers. The results of this study showed that microplastic particles are present in the sediments of Khor Musa and most of these particles are filamentous and with dimensions of less than 100 micrometers. This means that the adsorption capacity of these particles is high for pollutants.