This study presents a risk-based decision support framework for seismic retrofit of building structures where the decision criterion is to minimize the sum of the cost required for the rehabilitation and the expected seismic loss over a specified time period. Probabilistic seismic hazard model (PSHM) and probabilistic seismic demand model (PSDM) are utilized for manipulation of the uncertainty propagation from the seismic hazard to the structural damage. A mathematical formula is then developed for probabilistic estimation of the seismic damage and losses over a specified time period. The analysis procedure is developed such that the effect of the different configurations of the decision inputs can be promptly observed. The proposed procedure is demonstrated by performing a decision analysis for a hypothetical RC building structure for determination of the optimal level of seismic rehabilitation using steel bracings.