The men's 400 metres event at the 2003 IAAF World Indoor Championships was held on March 14–16.
| Gold | Silver | Bronze |
Tyree Washington  United States
|
Daniel Caines  Great Britain
|
Paul McKee  IrelandJamie Baulch Great Britain
|
First 2 of each heat (Q) and next 4 fastest (q) qualified for the semifinals.
| Rank | Heat | Name | Nationality | Time | Notes |
|---|---|---|---|---|---|
| 1 | 1 | Daniel Caines | Great Britain |
45.85 | Q |
| 2 | 1 | Tyree Washington | United States |
45.90 | Q, PB |
| 3 | 4 | Daniel Batman |  Australia |
46.11 | Q |
| 4 | 1 | Marek Plawgo |  Poland |
46.33 | q |
| 5 | 2 | David Canal |  Spain |
46.39 | Q |
| 6 | 3 | Jamie Baulch | Great Britain |
46.44 | Q |
| 7 | 1 | Sofiane Labidi |  Tunisia |
46.47 | q, NR |
| 8 | 2 | Paul McKee | Ireland |
46.68 | Q |
| 9 | 3 | David McCarthy | Ireland |
46.69 | Q |
| 10 | 3 | Chris Brown |  Bahamas |
46.74 | q |
| 11 | 3 | Cedric van Branteghem |  Belgium |
46.75 | q |
| 12 | 4 | Ioan Lucian Vieru |  Romania |
46.84 | Q |
| 13 | 4 | Damion Barry |  Trinidad and Tobago |
47.21 | |
| 14 | 2 | Edoardo Vallet |  Italy |
47.77 | |
| 15 | 2 | California Molefe |  Botswana |
47.90 | NR |
| 16 | 4 | Dmitriy Chumichkin |  Azerbaijan |
48.11 | |
| 17 | 2 | Ernie Candelario |  Philippines |
48.86 | |
| 18 | 3 | Román Basil |  Panama |
49.46 | |
| 1 | Rohan Pradeep Kumara |  Sri Lanka |
DQ | ||
| 2 | Davian Clarke |  Jamaica |
DQ | ||
| 3 | Moses Kondowe |  Malawi |
DQ | ||
| 4 | Corey Nelson | United States |
DQ | ||
| 4 | Alleyne Francique |  Grenada |
DQ | ||
| 1 | Danny McFarlane | Jamaica |
DNF |
First 2 of each semifinal (Q) qualified directly for the final.
| Rank | Heat | Name | Nationality | Time | Notes |
|---|---|---|---|---|---|
| 1 | 1 | Paul McKee | Ireland |
46.24 | Q, NR |
| 1 | 2 | Daniel Caines | Great Britain |
46.24 | Q |
| 3 | 2 | Tyree Washington | United States |
46.50 | Q |
| 4 | 2 | David McCarthy | Ireland |
46.61 | Q, PB |
| 5 | 1 | Jamie Baulch | Great Britain |
46.74 | Q |
| 6 | 1 | Daniel Batman | Australia |
46.76 | Q |
| 7 | 2 | Marek Plawgo | Poland |
46.82 | |
| 8 | 1 | Ioan Lucian Vieru | Romania |
47.01 | |
| 8 | 2 | Cedric van Branteghem | Belgium |
47.01 | |
| 10 | 1 | Chris Brown | Bahamas |
47.03 | |
| 11 | 1 | Sofiane Labidi | Tunisia |
47.14 | |
| 12 | 2 | David Canal | Spain |
47.17 |
| Rank | Name | Nationality | Time | Notes |
|---|---|---|---|---|
 |
Tyree Washington | United States |
45.34 | WL |
 |
Daniel Caines | Great Britain |
45.43 | PB |
 |
Paul McKee | Ireland |
45.99 | NR |
| |
Jamie Baulch | Great Britain |
45.99 | SB |
| 5 | David McCarthy | Ireland |
46.61 | PB |
| 6 | Daniel Batman | Australia |
46.67 |