The water quality index (WQI) is a practical and comprehensive technique to evaluate water quality. It is often employed to assess water quality in simple terms and determine its suitability for various uses. The current study aimed to assess the temporal and spatial variation of the Al-Dujaila River. Three sites were selected for surveying from January to December 2021. The studied area starts after the AL-Kut dam and goes to the point where the river exits in the city of AL-Kut. Several physico-chemical parameters were addressed to calculate the IQ-WQI based on the Iraqi rivers maintaining limits; namely, dissolved oxygen (DO mg/ l), biological oxygen demand (BOD₅ mg/l), hydrogen ion (pH), phosphate (PO₄ mg/ l), nitrate (NO₃ mg/ l), chloride (Cl mg/ l), sulfate (SO₄^-2  mg/ l), total dissolved solid (TDS mg/ l), and turbidity (Turb NTU). The concentrations of most parameters were within the standard limits, except for SO₄^-2, TDS, and Turb, where the highest concentrations reached 390mg/ l, 920mg/ l, and 70 NTU, respectively. The rating of the water quality index in these three sites falls under very poor water quality, where values of the IQ-WQI ranged between 83.41– 89.48 in the wet season, and in the dry season, the value was 85.24– 91.13. The shift of the index toward the worst conditions is related to the high concentration of TDS and SO4-2, where the standard limits for them are 500 and 200mg/ l according to the Iraqi rivers maintaining limits, respectively, which indicates pollution conditions of the river caused by the increased levels of salts. The principal component analysis (PCA) was used to visualize the data obtained to know how they interrelate in addition to extracting the most affecting parameters on water quality.