Mayor Michael Bloomberg proposed legislation Monday that would prohibit citywide retailers from showing tobacco products, a proposal that would make New York the first city in the nation to ban cigarette displays.

Under legislation set to be introduced in the City Council this week, sellers would be required to keep tobacco products out of sight except during a purchase by an adult or during restocking. Tobacco products would be required to be kept in cabinets, drawers, under the counter, behind a curtain or in any concealed...