The series follows the exploits of the Impossible Missions Force (IMF), a small team of secret agents used for covert missions against dictators, evil organizations, and crime lords. On occasion, the IMF also mounts unsanctioned, private missions on behalf of its members.

The identities of the organization which oversees the IMF and the government it works for are never revealed. Only rare cryptic bits of information are ever provided during the life of the series, such as in the third season mission "Nicole", where the IMF leader states that his instructions come from "Division Seven". In the 1980s revival, it is suggested the IMF is an independent agency (as the FBI is legally bound to operate only within the U.S. and the CIA is restricted to only conduct its business outside the country). However, in the first motion picture film, the IMF is depicted as part of the CIA.