A detailed evaluation for the use of treated petroleum refinery wastewater in irrigation of Gerbera plants, vegetative growth, production and chemical compounds of Gerbera jamesonii were determined. The experiment was conducted for two successive seasons of 2014 and 2015 at the Floriculture Nursery under full sunlight conditions at Horticulture Research Institute, Ornamental Plants and Landscape Gardining Research Department, Egypt using clay loam soil and 30 cm pots. The mean plant height in harvest was 32.33 +1.86 and 25.67+ 2.18 cm for irrigation with treated wastewater at the first and second seasons respectively. Mean number of roots /plant in harvest was 42.33 +5.5 and 42.67+ 2.03 for irrigation with treated wastewater at the first and second seasons respectively. Mean flowers number / plant in harvest were 6.42 +1.1 and 6.81+ 1.3 for irrigation with treated wastewater at the first and second seasons respectively. Mean flower diameters in harvest were 7.44 +1.14 and 7.1+ 1.18 cm for irrigation with treated wastewater at the first and second seasons respectively. The mean numbers of leaves / plant in harvest were 8.33 +0.37 and 6.0+ 1.0 for irrigation with treated wastewater at the first and second seasons respectively.