Water Quality of Mahrut River, passing through Muqdadiyah, a city in Diyala, Iraq, was evaluated for irrigation using the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI). Water samples were collected from six sites during two seasons, summer and winter in 2010-2011. Index scores were determined for fifteen constituents (pH, EC, HCO3, Cl, Sodium Absorption Ratio (SAR), Soluble Sodium Percentage (SSP), Residual Sodium Carbonate (RSC), Cd, Cr, Cu, Fe, Pb, Mn, Ni and Zn). The results of the calculated CCME WQI indicated that water quality of Mahrut River was marginal condition for irrigation in the 1st site while it was poor condition in the other sites. It is suggested that monitoring of the river is necessary for proper management to solve pollution problems in the river system.