This research was conducted to study the role of arbuscular mycorrhiza fungi (AMF) in response to different irrigation water sources on Nemesia (Nemesia × hybridus) plants. Three sources of irrigation water (tap-water, treated waste-water, and well-water) were tested on positive and negative-mycorrhizal plants with decontaminated soil in pots. This study presented that irrigation with waste-water increased growth parameters, mineral composition, gas exchange parameters, photosynthetic pigments, and leaf water status indicators. For all sources of irrigation water, mycorrhizal inoculation significantly increased all studied parameters. Transpiration rate, intercellular CO2 concentration, and net photosynthesis rate of the negative-mycorrhizal plants was lower than those of positive-mycorrhizal plants. The majority of the vegetative growth, flower yield, mineral composition, leaf water status, and photosynthetic parameters varied with the mycorrhizal colonization. The results of this research provide strong indication that AMF inoculation can improve flower yield and growth quality of Nemesia plants. This is seen particularly in plants irrigated with treated waste-water that had improved mineral uptake, photosynthetic status, and leaf water relations. This study recommends irrigation with treated waste-water with + AMF inoculation for Nemesia production. AMF will enhance the response of the plant to irrigation with treated waste-water and reduce the cost associated with using other water sources.