The Women's 400m Freestyle event at the 2003 Pan American Games took place on August 14, 2003 (Day 13 of the Games).
| 4:03.85 | 1988-09-22 | ||||
| 4:10.60 | 1979-07-01 | San Juan, Puerto Rico |
| Place | Swimmer | Heats | Final | ||
|---|---|---|---|---|---|
| Time | Rank | Time | |||
| 1 | 4:16.26 | 1 | 4:10.18 GR | ||
| 2 | 4:16.93 | 2 | 4:13.03 | ||
| 3 | 4:19.72 | 5 | 4:14.21 | ||
| 4 | 4:18.30 | 3 | 4:14.85 | ||
| 5 | 4:19.39 | 4 | 4:15.99 | ||
| 6 | 4:21.04 | 7 | 4:17.73 | ||
| 7 | 4:19.83 | 6 | 4:18.24 | ||
| 8 | 4:24.41 | 9 | 4:23.37 | ||
| 9 | 4:24.45 | 10 | 4:21.57 | ||
| 10 | [1] | 4:24.25 | 8 | 4:22.79 | |
| 11 | 4:28.32 | 11 | 4:26.79 | ||
| 12 | 4:30.25 | 12 | 4:28.73 | ||
| 13 | 4:31.35 | 13 | 4:29.57 | ||
| 14 | 4:37.42 | 14 | 4:34.60 | ||
| 15 | 4:39.56 | 15 | 4:36.52 | ||
| 16 | 4:42.48 | 16 | 7:19.53 | ||