The objective of this paper is to present a multiagent system (MAS) that can enable integration of a number of IoT devices to allow grid-interactive and intelligent building operation. The proposed platform called BEMOSS — Building Energy Management Open Source Software is developed toallow sensing and control of HVAC, lighting and plug load controllers in small- and medium-sized commercial buildings. The main objectives are toimprove energy efficiency, reduce energy consumption, and foster demand response (DR) implementation in buildings with OpenADR protocol. Functionalities of BEMOSS software platformand its integration with IoT devices are demonstrated in a laboratory test bed located at Virginia Tech Advanced Research Institute. Future research directions are also discussed.