An Associated Press photographer at the scene saw the man's lifeless body covered with a tarp on a blood-covered sidewalk in the Zona Rosa, an area crowded with hotels and restaurants.
An official of the city's Public Safety Department confirmed the man was shot to death. Under department rules, the official was not authorized to be quoted by name.
The official said that one of two men on a motorcycle fired several shots at the man and then drove off.
Assassins commonly use motorcycles in Central America, but that has been less common in Mexico.
Mexico City has largely been spared the drug violence plaguing many parts of the country.