Although treated wastewater (TWW) is increasingly being used to irrigate urban landscapes in arid regions like Qatar to preserve scarce freshwater resources, little is known about its long-term ecological impacts. The effects of extended irrigation with TWW on the composition of weed communities and soil characteristics in urban turfgrass systems were assessed in this study for a full year period. Three turfgrass fields in public parks in Doha that are not distant and similar in turf species and type of management were chosen. One of them has received regular tap water, and the other two had received a period of two years or a period of seven years irrigation with TWW. Due to nutrient availability in TWW, long-term irrigation improved turfgrass performance but drastically changed the structure and composition of the weed communities. More weed diversity and abundance were observed under irrigation with TWW, coinciding with cumulative increases in soil salinity [from 265 & micro;S/cm for soil irrigated with regular tap water to about 1799 & micro;S/cm for soil long-term irrigated with treated wastewater] and nutrient levels. Dactyloctenium aristatum and Euphorbia prostrata were dominating the field under TWW irrigation, while Cyperus rotundus prevailed better under regular tap-water irrigation. Crucially, build-up of toxic elements was found in the turfgrass, but not harmful. Overall, the findings showed that although TWW is a useful source for maintaining urban green spaces in arid regions, its long-term use necessitates cautious management to reduce weed growth and adaptation. Maintaining sustainable and healthy urban landscapes may be aided by using salt-leaching irrigation techniques and seasonal blending with freshwater.