A method of obtaining crystallized monoammonium phosphate of good quality using Jordanian granular diammonium phosphate (18 wt% N and 46 wt% P2O5) and impure wet process phosphoric acid (about 50 wt% P2O5) is presented. About 84 % of the total P2O5 fed to the reactor as dissolved diammonium phosphate and impure wet process phosphoric acid is recovered as crystalline monoammonium phosphate of about 11 wt% N and 62 wt%P2O5, the obtained crystals are quadratic prisms in shape. The main steps of the production process include dissolution, filtration, reaction, crystallization, centrifuging, and then drying. It is found that the best operating conditions to produce monoammonium phosphate of good quality, quantity, and crystals size are: 1:1 as DAP/water weight ratio, 1:1 H3PO4/DAP mole ratio, 3 h dissolution time, 35 °C reaction temperature, 45 min reaction time, 15 °C crystallization temperature, 90 min crystallization time, and 70 rpm agitation speed in both the reactor and crystallizer.