A reservoir theory has been used to investigate the spontaneous emission of a two-level atom in a Kerr nonlinear blackbody. It is found that the atomic decay rate is a monotonically increasing function of absolute temperature. Below a transition temperature
Tc, the spontaneous emission is always inhibited compared to that in a nonabsorbing linear medium. It is also found that the inhibition of spontaneous emission is a monotonically decreasing function of the Kerr nonlinear coefficient. The inhibition of spontaneous emission is interpreted on the basis of a physical mechanism.