Thewomen's400 metres event at the2003 IAAF World Indoor Championships was held on March 14–16.
| Gold | Silver | Bronze |
Natalya Nazarova Russia | Christine Amertil Bahamas | Grit Breuer Germany |
First 2 of each heat (Q) and next 2 fastest (q) qualified for the semifinals.
| Rank | Heat | Name | Nationality | Time | Notes |
|---|---|---|---|---|---|
| 1 | 3 | Natalya Nazarova | Russia | 51.24 | Q |
| 2 | 3 | Catherine Murphy |  Great Britain | 51.89 | Q, SB |
| 3 | 1 | Tonique Williams-Darling | Bahamas | 52.04 | Q, PB |
| 4 | 5 | Grit Breuer | Germany | 52.10 | Q |
| 5 | 2 | Christine Amertil | Bahamas | 52.15 | Q |
| 6 | 4 | Sviatlana Usovich |  Belarus | 52.20 | Q |
| 7 | 5 | Sandie Richards |  Jamaica | 52.46 | Q |
| 8 | 1 | Yuliya Pechenkina | Russia | 52.62 | Q |
| 9 | 5 | Grażyna Prokopek |  Poland | 52.72 | q,NR |
| 10 | 1 | Jennifer Meadows | Great Britain | 52.74 | q, PB |
| 11 | 2 | Monique Hennagan |  United States | 52.83 | Q |
| 12 | 4 | Aliann Pompey |  Guyana | 52.86 | Q, SB |
| 13 | 4 | Kaltouma Nadjina |  Chad | 53.50 | |
| 14 | 1 | Sandrine Thiébaud-Kangni |  Togo | 53.51 | |
| 15 | 1 | Monika Niederstatter |  Italy | 53.57 | |
| 16 | 2 | Karen Shinkins |  Ireland | 53.59 | |
| 17 | 4 | Antonina Yefremova |  Ukraine | 53.64 | |
| 18 | 2 | Carmo Tavares |  Portugal | 53.65 | |
| 19 | 3 | Ronetta Smith | Jamaica | 53.66 | SB |
| 20 | 5 | Awatef Ben Hassine |  Tunisia | 54.01 | |
| 21 | 5 | Geisa Aparecida Coutinho |  Brazil | 54.23 | |
| 22 | 1 | Tiffany Barnes | United States | 54.38 | |
| 23 | 3 | Maria Teresa Schutzmann | Italy | 54.51 | |
| 24 | 2 | K.V.Damayanthi Dharsha |  Sri Lanka | 54.61 | |
| 25 | 5 | Yvonne Harrison |  Puerto Rico | 56.17 | |
| 26 | 2 | Klodiana Shala |  Albania | 57.81 | |
| 27 | 4 | Salhate Djamaldine |  Comoros | 58.88 | |
| 3 | Mireille Nguimgo |  Cameroon | DQ | ||
| 4 | Karla Hernández |  El Salvador | DQ |
First 2 of each semifinal (Q) qualified directly for the final.
| Rank | Heat | Name | Nationality | Time | Notes |
|---|---|---|---|---|---|
| 1 | 1 | Natalya Nazarova | Russia | 50.90 | Q |
| 2 | 1 | Christine Amertil | Bahamas | 51.11 | Q,NR |
| 3 | 2 | Grit Breuer | Germany | 51.56 | Q, SB |
| 4 | 2 | Catherine Murphy | Great Britain | 51.74 | Q, PB |
| 5 | 2 | Monique Hennagan | United States | 51.89 | Q, PB |
| 6 | 1 | Sviatlana Usovich | Belarus | 52.18 | Q |
| 7 | 1 | Sandie Richards | Jamaica | 52.20 | SB |
| 8 | 1 | Aliann Pompey | Guyana | 52.74 | SB |
| 9 | 2 | Grażyna Prokopek | Poland | 53.07 | |
| 10 | 1 | Jennifer Meadows | Great Britain | 53.36 | |
| 2 | Yuliya Pechenkina | Russia | DQ | ||
| 2 | Tonique Williams-Darling | Bahamas | DQ |
| Rank | Name | Nationality | Time | Notes |
|---|---|---|---|---|
 | Natalya Nazarova | Russia | 50.83 | |
 | Christine Amertil | Bahamas | 51.11 | NR |
 | Grit Breuer | Germany | 51.13 | SB |
| 4 | Catherine Murphy | Great Britain | 51.99 | |
| 5 | Monique Hennagan | United States | 52.08 | |
| 6 | Sviatlana Usovich | Belarus | 52.72 |
