Existing reinforced concrete frame buildings designed for vertical loads only could suffer severe damage during earthquakes. In recent years, many research activities were undertaken to develop a reliable and practical analysis procedure to identify the safety level of existing structures. The Incremental Dynamic Analysis (IDA) is considered to be one of the most accurate methods to estimate the seismic demand and capacity of structures. However, the executions of many nonlinear response history analyses (NL_RHA) are required to describe the entire range of structural response. The research discussed in this paper deals with the proposal of an efficient Incremental Modal Pushover Analysis (IMPA) to obtain capacity curves by replacing the nonlinear response history analysis of the IDA procedure with Modal Pushover Analysis (MPA). In this work, first, the MPA is examined and extended to three-dimensional asymmetric structures. Than, it is incorporated into the proposed procedure (IMPA) to estimate the structure’s seismic response and capacity for given seismic actions. This new procedure, which accounts for higher modes effects, does not require the execution of complex NL-RHA, but only a simpler nonlinear static analysis. Finally, the extended MPA and IMPA were applied to an existing irregular framed building.