Het seizoen 4 van Mission: Impossible werd uitgezonden op CBS van dimanche 28 septembre 1969 tot dimanche 29 mars 1970. Het bestaat uit 26 afleveringen, de eerste heet "The Code" en de laatste "The Martyr".
Elite special agents undertook top-secret assignments in crackerjack episodes, which kicked off with the team leader receiving instructions via a tape-recorded message that self-destructed in five seconds. What followed were usually breakneck spyjinks set to a pulsating Lalo Schifrin score. Martin Landau turned down the Spock role in 'Star Trek' to play IMFer Rollin Hand. When Landau left the series in 1969, his replacement was the man who built a career on Spock, Leonard Nimoy.