Swimming at the 2009 Southeast Asian Games – Women's 400 metre individual medley
# Swimming at the 2009 Southeast Asian Games – Women's 400 metre individual medley

The Women's 400 Individual Medley (or "I.M.") swimming event at the 2009 SEA Games was held in December 2009.

The Games Record at the start of the event was 4:51.87, swum by Joscelin Yeo at the 1999 SEA Games (on August 13).

## Results

### Final

| Place | Swimmer | Nation | Time |
| - | - | - | - |
| 1 | Natthanan J. | Thailand | 4:55.07 |
| 2 | QUAH Ting Wen | Singapore | 4:56.32 |
| 3 | Hui Yu Koh | Singapore | 4:56.73 |
| 4 | Fibriani Marita | Indonesia | 4:57.16 |
| 5 | Chavisa T. | Thailand | 4:58.30 |
| 6 | SIOW Yi Ting | Malaysia | 5:05.45 |
| 7 | T Kim Tuyen Nguyen | Vietnam | 5:05.45 |
| 8 | Ressa Ressa | Indonesia | 5:17.78 |

### Preliminary heats

| Rank | Swimmer | Nation | Time | Notes |
| - | - | - | - | - |
| 1 | Fibriani Marita | Indonesia | 5:09.82 | Q |
| 2 | SIOW Yi Ting | Malaysia | 5:11.21 | Q |
| 3 | Chavisa T. | Thailand | 5:13.84 | Q |
| 4 | Natthanan J. | Thailand | 5:18.71 | Q |
| 5 | Ressa Ressa | Indonesia | 5:19.18 | Q |
| 6 | QUAH Ting Wen | Singapore | 5:19.06 | Q |
| 7 | Hui Yu Koh | Singapore | 5:20.33 | Q |
| 8 | T Kim Tuyen Nguyen | Vietnam | 5:27.06 | Q |
| 9 | Wei Li Lai | Malaysia | 5:27.23 | |
