Madeira Beach, Florida. Not to be confused with Madeira. Madeira Beach /məˈdɛərə/ mə-DAIR-ə beach is a city in Pinellas County, Florida, United States, bordered on the west by the Gulf of Mexico and on the east by St. Petersburg. As of the 2010 census, the population was 4,263. The area is primarily residential with little or no industrial or sizable service businesses.