The Women's 4x100m Medley Relay event at the 2003 Pan American Games took place on August 16, 2003 (Day 15 of the Games).
| 3:58.30 | 2000-09-23 |  Sydney, Australia | |||
| 4:06.08 | 1999-08-06 |  Winnipeg, Canada |
| Place | Nation | Swimmers | Heats | Final | |
|---|---|---|---|---|---|
| Time | Rank | Time | |||
| 1 | 4:09.80 | 1 | 4:05.92 GR | ||
| 2 | 4:18.36 | 2 | 4:13.72 | ||
| 3 | 4:32.19 | 5 | 4:18.04 | ||
| 4 | 4:25.30 | 3 | 4:18.29 | ||
| 5 | ♦ ♦ ♦ ♦ | 4:33.30 | 6 | 4:29.74 | |
| 6 | ♦ ♦ ♦ ♦ | 4:34.24 | 7 | 4:31.47 | |
| 7 | ♦ ♦ ♦ ♦ | 4:39.92 | 8 | 4:40.05 | |
| 8 | ♦ ♦ ♦ ♦ | 4:30.39 | 4 | DQ | |
| - | ♦ ♦ ♦ ♦ | DQ | - | ||