We propose an age–space structured brucellosis model that includes diffusion with heterogeneous coefficients and a general nonlinear incidence rate. The renewal process is used to calculate the next generation operator, and the basic reproduction number R 0 is defined by the spectral radius of the next generation operator. We prove that R 0 governs the threshold dynamics of the brucellosis model: when R 0 < 1 the disease dies out, and when R 0 > 1 the disease persists.