It dramatizes the killing of exiled Soviet revolutionary Leon Trotsky by NKVD agent Frank Jacson in Mexico City in 1940.

It stars Richard Burton as Trotsky and Alain Delon as Jacson, along with Romy Schneider, Valentina Cortese, and Jean Desailly.

[6] According to author Melvin Bragg, the director Joseph Losey was so drunk and tired that he relied on long monologues by Burton to carry the film, in some cases even forgetting what was in the script.

A Shakespearian theme may be detected in Losey’s treatment, in “the peculiar bond between the victim and his assassin.”[10] Making the general observation that Losey’s oeuvre lacks “thematic continuity,” critic Roger Greenspun at the New York Times praises The Assassination of Trotsky for its “audacity and imaginative density.” Greenspun notes that there are numerous devices in the film “not to be excused, ” among these the inclusion of “nostalgic Wordsworthian” excerpts from Trotsky’s personal journals inserted into the script.

Her role is comparatively small, but I think it is the loveliest performance in the movie.”[11] The Monthly Film Bulletin wrote: "Disconcertingly, any summary of the bizarre circumstances of Trotsky's death – the old man, once a prime mover in great events, screened from the world behind walls and watch towers until his confrontation with his impenetrable executioner – reads like a parody of a Losey movie...the characters in Trotsky seem to belong to no specific place or time: their relationships are founded on no shared code or natural necessity, but on the absurd chances of war and on blind collisions arising from their attempts to heave obsessions into actions that will move and change the world outside.

Losey seems to be trying to mask his indifference to the subject by retreating into a numb loftiness.”[13] Calling the film “a cold, unpleasant work,” arts editor David Walsh at the World Socialist Web Site disparages Losey’s characterization of the historical Trotsky: “Richard Burton is directed to play Trotsky as a pedantic, self-important and irritable windbag.” In contrast to his critique of Burton’s performance, critic Foster Hirsch confers fulsome praise on actor Alain Delon, in the role depicting Stalinist assassin Ramón Mercader (under his alias Frank Jacson in the film version): As the assassin, Alain Delon gives what is probably his finest performance, cold-eyed, wary, a figure of insinuating nervous energy.