The men's 400 metre individual medley event at the 1988 Summer Olympics took place between 20–21 September at the Jamsil Indoor Swimming Pool in Seoul, South Korea.

[1] Prior to this competition, the existing world and Olympic records were as follows.

The following records were established during the competition: Rule: The eight fastest swimmers advance to final A (Q), while the next eight to final B (q).

[2] [3]