The photoneutron spectra and ambient dose equivalent were determined in a radiotherapy room with a 15 MV linear accelerator using Monte Carlo simulation. A modified simple geometry of the accelerator's head was modeled by different simulations. Then, by putting it in a radiotherapy room, the photoneutron spectra at different distances from the isocenter and in the maze were determined. The source term spectrum is due to evaporation, and knock-on neutrons. In the presence of the walls, as the distance from isocenter is increased, evaporation and knock-on neutrons are reduced; however, epithermal and thermal neutrons tend to remain constant. The walls also play an influential role in increasing the photoneutron ambient dose equivalent. Subsequently, by placing this modified accelerator's head in the radiotherapy room, the coefficients of scattered and thermal fluences were also estimated.