The legislation makes New York the first large city or state in the country to prohibit sales to young adults.
During a bill-signing ceremony Tuesday, Bloomberg said the law will help prevent young people from experimenting with tobacco at the age when they are most likely to become addicted.
City health officials say 80 percent of smokers start before age 21.
Tobacco companies and some retailers had opposed the age increase. They say it will simply drive teenagers to the city's thriving black market.
More Nation & World Headlines
Ebola vaccine could stop virus in West Africa Wildfires rage in northern California What a six-foot 777 part might bring to MH370 mystery Purple Hearts in question after Chattanooga attack Lynn Anderson, singer of ‘Rose Garden,’ dies at 67 WWE Hall of Famer Roddy Piper dies at 61 Women advance to final phase of Army Ranger School Virginia may recall Confederate license plates
Our new comment system is not supported in IE 7. Please upgrade your browser here.