The Men's 4 × 100 m Medley Relay event at the 2003 Pan American Games took place on August 17, 2003 (Day 16 of the Games).
| 3:31.54 | 2003-07-27 |  Barcelona, Spain | |||
| 3:40.27 | 1999-08-07 |  Winnipeg, Canada |
| Place | Nation | Swimmers | Heats | Final | ||
|---|---|---|---|---|---|---|
| Time | Rank | Time | ||||
| 1 | 3:40.77 | 1 | 3:37.27 GR | |||
| 2 | 3:52.42 | 4 | 3:40.02 SA | |||
| 3 | 3:51.52 | 2 | 3:40.12 | |||
| 4 | ♦ ♦ ♦ ♦ | 3:53.26 | 5 | 3:45.34 | ||
| 5 | ♦ ♦ ♦ ♦ | 3:52.20 | 3 | 3:48.11 | ||
| 6 | ♦ ♦ ♦ ♦ | 3:58.15 | 8 | 3:51.98 | ||
| 7 | 3:57.44 | 7 | 3:53.57 NR | |||
| 8 | 3:56.07 | 6 | 3:55.00 NR | |||
| 9 | ♦ ♦ ♦ ♦ | 3:59.75 | 9 | |||