A nurse has pleaded guilty to murdering 11 elderly people by setting fire to the Sydney nursing home where he worked.

Roger Dean also pleaded guilty to causing grievous bodily harm to another eight nursing home residents injured by the blaze in 2011.

The 37-year-old registered nurse was on duty when he set fire to the nursing home.

He later appeared on television describing his efforts to rescue trapped people at the nursing home in the suburb of Quakers Hill.

Mr Dean made his pleas in New South Wales state Supreme Court earlier today.

His sentencing hearing starts on Thursday and he potentially faces life imprisonment.

Police had questioned him at the home hours before the blaze over theft allegations.

He has already pleaded guilty to stealing prescription drugs from the home.