Mr. Fenton Hardy
Frank and Joe could never keep a secret from their astute father, and they suspected that this was one of the abilities that made him such a successful investigator. Indeed, Fenton Hardy had made an enviable name for himself. For many years he had been a detective with the New York Police Department, but resigned to accept cases of his own. He is now known as one of the best private detectives in the country and has solved many mysteries that had baffled city detective forces.
Mrs. Laura Hardy
Laura Hardy, a pretty, petite woman, always worries about the dangers her husband and sons face, but has become accustomed to their hectic lifestyle.
Frank Hardy
Frank, a tall, dark-haired eighteen-year-old, is the more serious of the brothers. He likes to think things out, taking into account all aspects of a problem. He's good at analyzing clues and figuring out which are the logical steps to take in order to solve a case.
Joe Hardy
A year younger than his brother, Joe is almost Frank's complete opposite. He dashes into all kinds of situations without worrying too much about consequences, and refuses to admit that anything is impossible. Joe is full of enthusiasm and good humor, and can always be counted on to lighten up a tense situation with a witty remark.
Aunt Gertrude
Gertrude Hardy, a spinster of "uncertain years," is Fenton Hardy's sister. She never refrains from making her opinions known in the form of long tirades, but her prim visage is deceptive, for beneath her forbidding appearance, she is really one of the kindest people one could ever hope to meet.
Chet Morton
Chet, the Hardys' best friend, lives on a farm about a mile outside of Bayport. The pride of his life is an old yellow jalopy he nicknamed "Queen." Chet is rotund and freckle-faced, and loves to eat. Solving mysteries with the Hardys always gives him the jitters, but despite this, he is a loyal assistant and has often rescued them from dangerous predicaments. Chet is always picking up new hobbies, which sometimes play an instrumental part in solving a mystery.
Biff Hooper
Allen Hooper is a lanky, blond boy nicknamed Biff because of his fondness for a distant relative who is a boxer named Biff.
Tony Prito
Of Italian descent, Tony is lively and has a good sense of humour. His boat, the Napoli, is a good ship, but not quite a match for the Hardys' speedboat, the Sleuth. Tony's father is a contractor.
Phil Cohen
Phil is a quiet, intelligent boy who, in the newer books, is a computer genius.
Jerry Gilroy
Jerry, an excellent fielder on Bayport High's baseball team, is of medium height, wiry, and strong.
Iola Morton
Chet's sister was dark-haired and pretty. Joe Hardy thought she was the nicest girl in Bayport High and dated her regularly. Sadly, Iola was killed by a terrorist car bomb that was meant for Frank and Joe in Casefiles #1.
Callie Shaw
Callie is in Frank Hardy's class at Bayport High. Frank often dates the vivacious blonde, and likes her better than any other girl he knows.
Chief Collig
Ezra Collig, chief of the Bayport police force, is a tall, husky man well known to Fenton Hardy and his sons. Chief Collig often turns to the private detective for help solving particularly difficult cases.Con Riley
Patrolman Con Riley is a member of the Bayport police force.
Oscar Smuff
Probably the most annoying character in a Hardy Boys book, Smuff is a short, stout man who always wears a checkered suit and soft felt hat. He fancies himself a private detective but is often shown up by Frank and Joe despite his scorn for the two young detectives. In fact, Smuff often falls flat on his face while attempting to prove his worth as an investigator. (Before the books were revised, Smuff, along with Con Riley, was an inept detective with the Bayport police force.)
Sam Radley
Fenton Hardy's able operative. Sam and his wife, Ethel, live in an apartment in the center of town, about a half a mile from the Hardy home.
Jack Wayne
Lean-faced and tanned, Jack Wayne is Fenton Hardy's pilot on all his chartered flights. His plane is called the Skyhappy Sal.