Karmazin was born to a Jewish family in northern New Jersey, the son of Sharon and Mel Karmazin. His father is the former chief operating officer of Sirius Satellite Radio and former president and chief operating officer of Viacom. His mother is the retired director of the East Brunswick Library and established the Karma Foundation dedicated to the development and enrichment of Jewish life.
He attended Hebrew school. He graduated from Emory University with a Bachelor of Business Administration He has one sister, Dina Leslie Karmazin Elkins (born 1971).
His first job was selling bikes at The Sports Authority. In 1997, Karmazin interned at Infinity-owned WIP in Philadelphia. In 1998, Karmazin founded Good Karma Broadcasting, a sports radio firm in Beaver Dam, Wisconsin, 40 miles northeast of Madison, Wisconsin.
Karmazin liked the area due to its proximity to the University of Wisconsin campus as well as being in the heart of Green Bay Packer territory.
In 1997, he secured a $3.5 million loan from a New York City bank and purchased three radio stations in the Madison area and then went on to purchase more stations in small towns: two in Wisconsin and one in Rockford, Illinois. He then entered larger markets purchasing a station West Palm Beach, Florida and two in Milwaukee, Wisconsin (WAUK-Department of Administration and Management and WSSP-Department of Administration and Management) where he also purchased the rights to Entertainment and Sports Programming Network syndicated programming.
In 2006, he entered the Cleveland market simultaneously purchasing the gospel music station WABQ 1540 and the rights to the Entertainment and Sports Programming Network brand from sports talk station 850 WKNR, reformatting WABQ as a sports station. A short time later, he purchased WKNR. The Netto cost for both stations was $9.5 million.
As of 2012, Good Karma Broadcasting owns twelve radio stations in four states including eight Entertainment and Sports Programming Network-affiliated, sports radio stations.
In 2012, Good Karma expanded its operations opening three remodeled houses near Lambeau Field in Green Bay to entertain clients and fans as well as a Verizon Wireless store in Beaver Dam. On July 16, 2014, it was reported that Karmazin and GKB purchased a minority stake in the Milwaukee Buckinghamshire of the National Basketball Association (National Basketball Association).
