Seismic design of concrete structures is currently based on time-invariant capacity design criteria which do not account for environmental hazards. The significant progressive decay of strength and ductility of concrete structures exposed to damage, in particular due to reinforcing steel corrosion, shows that this approach should be revised to consider the deterioration over time of the seismic performance. This is particularly important for precast systems, for which most of the structural members may directly be exposed to the atmosphere and environmental aggressiveness. The paper addresses such problem and presents a general methodology for lifetime assessment of seismic performance of multi-storey precast buildings exposed to corrosion by taking into account the interaction between seismic and environmental hazards. The structural performance are evaluated at a cross-sectional level through the simulation of the diffusion process of aggressive agents and a proper modelling of the consequent damage due to corrosion. These results are used at the structural level to assess the life-cycle seismic performance by means of nonlinear static and dynamic analysis methods. The seismic performance are evaluated considering different limit states, including damage limitation and structural collapse. The methodology is formulated in probabilistic terms to account for the uncertainties involved in the problem. The effectiveness of the proposed approach is shown by application to multi-storey precast buildings. The results show that structures designed for the same seismic action could have different lifetime seismic performance depending on the environmental exposure. This emphasizes the importance of a life-cycle approach for both seismic assessment of existing buildings and seismic design of new structures, and indicates that capacity design criteria need to be properly calibrated in order to consider the severity of environmental exposure and the required structural lifetime.