The Kwun Tong Line, Tsuen Wan Line, Island Line and Tseung Kwan O Line are supported by their respective maintenance depots at Kowloon Bay, Tsuen Wan, Chai Wan, and Tseung Kwan O. Each provides a base for the 1,500 volt DC electric multiple unit (EMU) trains operating on the line they serve. The East Rail Line, Ma On Shan Line and West Rail Line are supported by maintenance depots respectively at Ho Tung Lau, Tai Wai and Pat Heung. Each provides a base for the 25kV AC EMU trains operating on the line they serve. The Light Rail is supported by the depot at Tuen Mun. The Airport Express, Tung Chung Line and Disneyland Resort Line are supported by the depot at Siu Ho Wan. The South Island Line is supported by the depot at Wong Chuk Hang.
Each depot has facilities for stabling, cleaning, preventive and corrective maintenance, as well as cranes and jacking facilities for replacement of heavy equipment.