A pot experiment was consummated under open field conditions at the nursery of Hort. Res. Inst., ARC., Giza, Egypt during 2015 and 2016 seasons to study the effect of spraying with gibberellic acid at 0, 500, 1000 and 1500 ppm concentrations (as a foliar spray 6 times with one month interval) and some fertilization treatments (without fertilization, NPK at 2 g/pot and phosphorein at 5 g/pot as soil drench) and their interactions on vegetative, flowering, root growth and chemical composition of 3-months-old Bougainvillea glabra plants grown in 20-cm-diameter plastic pots filled with a mixture of sand, loam and peatmoss (1:1:1, v:v). The obtained results indicated that all fertilization treatments significantly improved all vegetative, flowering and root growth traits of the plants compared to control, especially the interaction treatments between NPK at 2 g/pot and gibberellic acid at 1500 ppm in all vegetative growth characters, leaves content of chlorophylls a and b, carotenoids and total carbohydrates, N, P and K % followed by the plants treated with phosphorein at 5 g/pot as a soil drench and GA₃ at 1500 ppm. Hence, in order to get the best growth and high quality plants, it is recommended to treat the plants with NPK at 2 g/pot and spraying the foliage till run-off with 1500 ppm of GA₃ solution 6 times with one month interval.