The board also selected founding father Benjamin Franklin for membership in the hall.
Both will be formally inducted in October at the DMA's 87th annual conference in New Orleans.
"The significant contributions made by both of these leaders continue to propel the industry forward," said H. Robert Wientzen, DMA president-CEO, in a statement.
The DMA said Florence is credited with, among other things, developing the first direct mail prospecting database, which b-to-b mailers continue to use.
Franklin (1709-1790) was a direct marketer of scientific and academic books. He is believed to have been the first cataloger in the U.S., and his selection for the Hall of Fame is based on contributions made to the mail-order marketing industry.