Ethiopian agriculture, the primary sector used to achieve food security, has been challenged byfrequent droughts. To alleviate this problem, the government emphasizes the development of the irrigation sub-sector. But the continuous assessment of the irrigation water quality is one of theforeseeable challenges. The objective of this study was to assess the physicochemical, biologicalquality, and the level of metal cations of irrigation water of Koga irrigation project, MechaDistrict, Amhara Region, Ethiopia. Thirteen water samples were collected and analyzed for eleven physicochemical, three biological parameters, and three major metal cations. Thephysicochemical parameters and metal cations were determined using standard procedures.Themembrane filtration method was used for bacteriological water quality analysis. Sodium absorption ratio (SAR), Magnesium hazard(MH), and Kelley’s ratio(KR) were determined usingthe laboratory results. The turbidity, total suspended solids (TSS), total alkalinity (TA), and total hardness (TH) surpassed the recommended limit of FAO and didn’t fit international qualitystandards of irrigation water. The SO 4 2- , PO 4 3- , and BOD levels of all samples crossed the FAOthreshold limit and didn’t fit the greywater used for irrigation. The TDS, EC, pH, NO 5 , and coliform levels were to some extent satisfactory. The levels of most of the water qualityparameters were found to be above the tolerance limit of the major crops grown in the area. Asthe data obtained, the concentration of Na + (2.20-24.67 mg/L) and Mg (55-81 mg/Lsignificantly increased as compared to the reported values (3.5-3.7 mg/L Na , 11-42.5 mg/LMg 2+ ) in 2014. On the other hand, the concentration of Ca +2 (from nil to 3.99 mg/L) significantlydecreased from early reported values (0-110 mg/L) in 2012 and (12-23 mg/L) in 2014. This haresulted in an unsuitable proportion of Na + :Ca +2 and Mg 2+ :Ca 2+ , and magnesium hazard was anticipated. Although studies with seasonal variations and more samples need to be taken todraw concrete conclusions, this study revealed that most of the studied irrigation water qualityparametres of Koga irrigation water were not found within the limits of FAO and internationalirrigation water quality guidelines. Therefore, the water quality managers, the people in thearea, the Koga irrigation office together with the concerned bodies should do remedial actions so that the pollution load on the irrigation water of Koga irrigation project can be reduced. 2+ + 3 -