Smart buildings and plug-in hybrid vehicles (PHEVs) are two emerging novel technologies because of their potential economic and environmental benefits. Integrating PHEVs into building energy management has the potential of improving the energy and comfort management in a building environment. Considering that the user expectation of a PHEV is to finish the next trip with a minimum cost of gasoline after unplugging, an intelligent PHEV control system utilizing multi-agent technology is proposed. Graphical User Interface (GUI) offers flexibility to customers by allowing them to specify their driving patterns and monitor the results. By wisely managing the charging and discharging patterns of PHEVs, the proposed system is capable of increasing the building's overall comfort level while reducing the PHEVs' total cost of gasoline. Case study and simulation results are presented and discussed in this paper.