Famous fictional Private Investigators rely on powers of deduction/rationalization and educated thought to solve crimes. These characters have long been a staple of detective mystery crime fiction, particularly in detective novels and short stories set in Britain and written during the "Golden Age of Detective Fiction" (1920s-1930s). They are often popularized as individual characters rather than parts of the fictional work in which they appear.

One of the first private investigator new zealand famous Private Investigators in fiction was Arthur Conan Doyle's Sherlock Holmes. Others included Miss Marple, Lord Peter Wimsey, Poirot and Jim Rockford. It was not until the prosperity of the 1920s that the Private Investigator became accessible to the average citizen.

In Great Britain, it has been suggested that the Private Investigator was operating well before the Metropolitan Police Force was formed more than 100 years ago. The formation of the Police Force may have been hastened by the unscrupulous activities of some of these Private Investigators. While the ethics and character of many of those earlier Private Investigators was open to criticism, today's Private

Investigator is generally honest, efficient, well-educated and aware of his moral and legal responsibilities.

The first Private Investigation agency was founded in 1833 by Eugene Vidocq, a French soldier and privateer. Because he hired ex-cons, law enforcement tried closing down his Office of Intelligence many times. Vidocq, despite some suspicious practices, is credited with introducing record-keeping, criminology and ballistics to criminal investigations. He made the first plaster casts of shoe impressions, created indelible ink and an unalterable bond paper. In the US, the Pinkerton National Detective Agency was a detective agency, established in 1850 by Allan Pinkerton. Pinkerton had become famous when he foiled a plot to assassinate then President-Elect Abraham Lincoln. During the height of its existence, the Pinkerton Detective Agency had more agents than the standing army of the United States of America, causing the state of Ohio to outlaw the agency, due to the possibility of its being hired out as a "private army" or militia. The agency's logo, an eye embellished with the words "We Never Sleep" inspired the term "private eye.

Since then the private detective industry has grown with the changing needs of the public. Social issues like infidelity and unionization have impacted the industry and created new types of work, as has the need for insurance, and with it insurance fraud, criminal defense investigations, the invention of low cost listening devices and more.