The 1978 film version of Agatha Christie's Death on the Nile starring Peter Ustinov will see a crucial scene cut out in future airings before the watershed at 9pm.
The scene in question sees character Jackie de Bellefort - played by Mia Farrow - shoot herself in the head after killing her lover.
One viewer complained about the violent death, after it was shown at 3.30pm on Saturday, March 17.
The move to censor it has arrived despite hundreds of airings over the years, including 20 showings before 9pm since 2004 alone.
Ofcom's decision ruled: "Her suicide was shown in some detail and was not appropriately limited.
"Given the Saturday afternoon scheduling of this film, our assessment was that it was likely that a significant number of children would have been watching ITV's main and public service channel at this time."
Audience figures showed that 71,000 viewers were under 16 during the time of the particular airing.
Its report continued: "While recognising the importance of including such a pivotal scene, we were concerned that the impact of the second gunshot was not edited or removed."
ITV responded that the scene was essential to the drama's plot, and that the work of Agatha Christie is not of particular interest to most children.
However, it added: "In keeping with our periodic review of pre-watershed material and in the light of viewer concerns, particularly those of parents, we undertook some additional editing of this scene for future daytime broadcasts."
A KFC advert was recently named the most complained-about television ad in British history.