The following work presents a methodology to optimize the absorption coefficients, conventionally considered as the main input parameters of room acoustical simulators. In the first place a presentation of the main characteristics of the acoustic simulator is made. Next, the procedure that is based on a modified “hill-climbing” approach is detailed. It performs the optimization of the coefficients value in an iterative procedure, which includes the calculation of the acoustic quality parameters (AQPs) with the results of an acoustic simulation of a real room. The AQPs from each simulation are compared with experimental measurements performed in the room, used as a reference for iterative adjustments. Finally, the results of the last iteration show a substantial reduction of the error, showing differences of 5.83% with the AQPs measured in the real room.