An additional 300 police officers will also be deployed and monitoring cameras installed, Anthony Williams, the mayor, announced on Friday.
The evening curfew applies to those under 17.
There have been 15 murders in the capital since the beginning of July.
In one incident, a British man was killed in the tourist area of Georgetown on July 9 by robbers who slashed his throat and attempted to rape the woman he was with.
The city will also launch a "violent crime task force" staffed by local police, FBI agents and officials from the Bureau of alcohol, tobacco, firearms and explosives (ATF).
Williams said: "The city is much safer than 10 years ago but we can do better."
But he said the crime rate in the capital was lower last year than at any point since the late 1960s.