The use of treated wastewater for irrigation purposes will be an essential component for sustainable water resources management, especially in the water-stressed countries as in Jordan. In this context, an attempt has been made to determine the suitability of effluent quality of selected wastewater treatment plants in Jordan for the irrigation purposes based on weighted arithmetic water quality index (WQI) approach, according to the Jordanian standards for reclaimed domestic wastewater. The effluent wastewater quality records from 22 wastewater treatment plants within a one-year-monitoring period from March 2015 to February 2016 were used. Fifteen physical, chemical, and microbiological parameters were selected to calculate WQI. According to the WQI scale classification, most of the selected wastewater treatment plants were not in full compliance with the Jordanian standards for the reclaimed domestic wastewater regarding the direct reuse of treated wastewater for the irrigation purposes. Therefore, for category A (i.e., vegetables that are normally eaten cooked, parking areas, sides of roads inside cities, and playgrounds), one plant is classified in the 'Excellent water' class and six plants as a "Good water" class. For category B (i.e., irrigation of fruit trees, green areas, and sides of roads outside the cities), one plant is classified in the 'Excellent water' class and twelve plants as a "Good water" class. For category C (i.e., irrigation of industrial crops, field crops, and forest trees), one plant is classified in the 'Excellent water' class and fifteen plants as a "Good water" class. The effective weight calculations identified that E. coli is considered the most effective parameter in the WQI values in category A, and to a lesser extent, SAR, pH, BOD, and NO3−. For category B, the SAR, pH and E. coli parameters are considered the most effective parameters in the WQI values. In turn, for category C, the SAR, pH, and PO4–3 parameters are considered the most effective parameters in the WQI values. Thus, these parameters based on category are considered as the main parameters which degrade the effluent wastewater quality for irrigation purposes. The results of this study are beneficial for the water managers and policymakers for proper actions on water resources and agricultural management in Jordan.