The current study has evaluated Shatt Al-Arab water using organic pollution index. The study included three stations, the first Al-Sharash, the second Al-Salhiya and the third area Al-Dweab. Water samples were monthly collected from December 2017 to November 2018. Five environmental parameters were used to calculate the organic pollution index (OPI) including Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Active nitrate (NO3), Ammonium ion (NH4) and Total Phosphate (TP). The highest biological oxygen demand was 9 mg.l-1 at Al-Sharash station in July and the lowest values 1mg.l-1 in the Al- Dweab station during December, January, February and April. The highest chemical oxygen demand (250 mg.l-1 was recorded at Al-Sharash station in September and the lowest value was 6.2 mg.l-1 in Al-Dweab station during December. Nitrates was recorded the highest value 41.51 mg nitrogen-nitrate.l-1 at Al-Salhiya station in May and lowest value 1.49 mg nitrogen- nitrate.l-1 at Al-Sharash station during December. The ammonium ion was recorded in highest value 7.7 mg.l-1 at Al- Salhiya station in December and the lowest value 0.5 mg. l-1 at Al-Sharash station during June, while phosphate value was 0.23 and 1.99 mg.l-1 were recorded at Al-Sharash station in August and July respectively. The highest value of organic pollution index was 2.56 at Al-Salihiya station in August and lowest value 0.69 in the Al-Dweab station in April, while the annual rate of organic pollution index for the first, second and third stations were 1.55, 1.81 and 1.47 respectively, and 1.61 for Shatt Al-Arab water.