AbstractThe rapid development of different energy production and conversion technologies at the distribution system (DS) level facilitates the integration of electrical, heating, and cooling DSs. The planning and operation of integrated DSs will affect the asset management of the transmission system (TS), which in turn will change the electrical energy prices and investment decisions at the DS level. This paper addresses a tri‐level multi‐stage approach for coordinated expansion planning of TS and integrated electrical, heating and cooling DSs. The photo voltaic panels (PVs), wind turbines (WTs), combined heat and power generation (CHP) units, boilers, and electrical and absorption chillers are considered investment candidates for coupling the DSs. Moreover, the expansion planning of TS lines, electrical feeders,and heating and cooling pipelines are integrated into the proposed model. The discussed model is tested on the modified 6‐bus, 30‐bus, and 118 bus IEEE TS comprising electrical, heating, and cooling DSs. The numerical study proves that the distribution system operators (DSOs), connected to different nodes of the TS, reduce their operation and emissioncosts by investing in the energy resources. Moreover, the proposed scheme successfully reduces the total expected cost of the transmission system operator (TSO) and successfully postpones the expansion of the TS.