"Another challenge for the Green Hornet, his aid Kato, and their rolling arsenal the Black Beauty. On Police records a wanted criminal, Green Hornet is really Britt Reid, owner-publisher of the Daily Sentinel, his duel identity known only to his secretary and the district attorney. And now, to protect the rights and lives of decent citizens, rides THE GREEN HORNET."

The character premiered in The Green Hornet, an American radio program that ran on WXYZ (a local Detroit station), the Mutual Broadcasting System and the network known through its succession of various owners as NBC Blue, the Blue Network and the ABC Network from January 31, 1936 to December 5, 1952. The juvenile adventure series initially starred Al Hodge in the title role, followed by Donovan Faust (1943), Robert Hall (1943-51) and Jack McCarthy (1951-52). The radio show used Rimsky-Korsakov's "Flight of the Bumblebee" as its theme song, blended with a hornet buzz created on a theremin.

The series detailed the adventures of Britt Reid, debonair newspaper publisher by day, crime-fighting masked hero at night. The vigilante nature of his operation quickly resulted in his being declared an outlaw himself, and Britt Reid decided to play to it. The Green Hornet became thought of as one of his city's biggest criminals, allowing him to walk into suspected racketeers' offices and ply them for information, or even demand a cut of their profits. He would be accompanied by his similarly masked but unnamed chauffeur/bodyguard/enforcer, who was also Reid's valet, Kato, initially described as a Japanese, and eventually as a Filipino. A widespread urban legend has been the claim that the show's writers switched from one nationality to the other immediately after the 1941 attack on Pearl Harbor, but the first disappeared well before direct U. S. involvement in the war, and the latter was not initially given until much later, with nothing more specific than "Oriental" being said in the interim. (When the characters were used in the first of a pair of movie serials, the politically perceptive producers of 1939 had Kato's nationality given as Korean.)

Whilst originally a radio show, the Green Hornet progressed to television, and the Hornet and Kato even made guest appearances in two episodes of Batman.