These 89 buses will cover almost all parts of the city and run between 11 pm and 5am.
The deployment started at a function attended by Transport Minister Ramakant Goswami.
"All the 89 buses, each having a home guard on board, started operation from tonight," a senior transport department official said.
The decision came a day after Delhi Chief Minister Sheila Dikshit in a meeting with Goswami and other officials decided to deploy home guards and to increase the services of night buses from existing 42 to 89.
The decision was a part of Delhi government's measures to enchance security of women in buses.
DTC operates a fleet of around 6,000 buses.