In this work, the effect of radiative heat transfer in the performance of a laboratory-scale hybrid rocket motor is investigated numerically. The radiative transport equation was included in the numerical model and was solved using the discrete ordinates method with S6 approximation. In the hybrid rocket motor with radiation model, the radiative heat flux is small compared to other heat fluxes, but the change in net flux due to inclusion of radiative heat flux corresponds to the change in the surface temperature and regression rate in the motor. The net heat flux into the fuel surface increased marginally at the beginning of the motor and decreased downstream in the motor when compared with the model without radiative heat transfer. The temperature and burn rate profiles also follow a similar trend in accordance with net heat flux. © 2021, Springer Nature Singapore Pte Ltd.