The present study aimed to investigate the relationship between benthic macrofauna and levels of organic pollution indicators (OPI) in the banks of Shatt al-Basrah Canal, Basrah, Iraq. The observed ranges of OPI and some water quality parameters were as follows: 1.58-3.9 for OPI, which were above the maximum acceptable pollution limit (1) in all months in Shatt al-Basrah Canal, 13-35.5°C for temperature, 49.9-21.8ppt for salinity, 1.15-5.21mg/ L for ammonium ion, 0.098-0.33mg/ L for phosphate values, 0.53-4.5mg/ L for nitrate values, 0.05-0.27mg/ L for nitrite values, 4.55-10.5 for dissolved oxygen (DO) and 7.2-8.2 for pH. A total of 25 species of benthic macroinvertebrates were collected. The monthly records of benthic macroinvertebrate species in the study area were relatively stable, from October 2023 to September 2024. The monthly changes in the density of benthic macroinvertebrates varied, with a maximum of 243 individuals in May and a minimum of 154 individuals in August. The highest annual total abundance was 599 for the bivalve group and the lowest abundance was 408 for the Cirripedia group. The relationship of OPI with different invertebrate groups varied, with a positive relationship with the bivalve group and Polycheta and a negative relationship with Gastropoda. Therefore, OPI is considered an indicator of pollution in the study area. Cirripedia and crustaceans did not show a clear relationship with organic pollution.