TNSTC is largest government bus transport corporation in India, following the bifurcation of APSRTC. It is fully owned and operated by Government of Tamil Nadu. It caters to all the districts within Tamil Nadu and also operates services to neighboring states of Andhra Pradesh, Karnataka, Kerala and union territory of Puduchery. Until 1996, transport corporation was bifurcated into 21 divisions which was later merged to form 8 divisions. School and college students get a free bus pass to travel on TNSTC buses. TNSTC owns 270 depots and five workshops. TNSTC also offers contract and tourist services. Every bus owned by the corporation displays a portrait of Tamil poet Thiruvalluvar along with a two line verse from Thirukkural inside the bus.
TNSTC and SETC uses custom made buses built on Ashok Leyland and TATA supplied chassis. Air conditioned buses for MTC are supplied by Volvo and TATA Marcopolo. All divisions have individual own coach building units.