The US internal security service, made up mostly of volunteers, helped restore order after Hurricane Katrina last August.
Mr Nagin made the request for at least 250 National Guardsmen to help patrol the streets of New Orleans after five teenagers were shot to death on Saturday.
Mr Nagin said his request followed a recent plea from New Orleans’ Police Chief Warren Riley for 60 Louisiana State Police troopers.
The National Guard would be used to patrol vast areas of the city that were heavily damaged "so we can put a policeman on every corner if necessary," Mr Nagin said.
He also vowed to do whatever he could to stop the violence that has killed 53 people so far this year including enforcing a curfew for youth, pursue funding for "night time basketball" to keep youngsters out of trouble and try to increase police pay to attract recruits.
Until recently, Chief Riley had asserted his 1,486 officers could protect the city, which has lost more than half of its 465,000 residents since Katrina struck on the 29th of August.
Police charged
Dozens of police officers deserted as gun-toting looters roamed the streets in the storm's aftermath.
The last guard patrols left New Orleans January 1, turning all law enforcement duties back over to local police.
However, the force has been hit by sporadic allegations of brutality and scandal with two veteran officers assigned to the French Quarter recently charged with armed robbery following an alleged operation at a massage parlour.
The New Orleans civil service commission has also began hearing the cases of nearly two dozen officers who are appealing disciplinary actions ranging from reprimands to dismissals.
The mayor and the city council have vowed to hold a crime summit in two weeks to seek more public input on how to stop the violence.