| Rank | Heat | Name | Nationality | Time | Notes
|
| 1 | 5 | Richards, SanyaSanya Richards | United States | 50.54 | Q
|
| 2 | 7 | Williams, SherickaShericka Williams | Jamaica | 50.57 | Q
|
| 3 | 7 | Firova, TatianaTatiana Firova | Russia | 50.59 | Q
|
| 4 | 2 | Grenot Martinez, LibaniaLibania Grenot Martinez | Italy | 50.87 | Q, NR
|
| 5 | 2 | Montsho, AmantleAmantle Montsho | Botswana | 50.91 | Q
|
| 6 | 5 | Pompey, AliannAliann Pompey | Guyana | 50.99 | Q, SB
|
| 7 | 1 | Whyte, RosemarieRosemarie Whyte | Jamaica | 51.00 | Q
|
| 7 | 4 | Ohuruogu, ChristineChristine Ohuruogu | Great Britain | 51.00 | Q
|
| 9 | 4 | Gushchina, YuliaYulia Gushchina | Russia | 51.18 | Q
|
| 10 | 1 | Amertil, ChristineChristine Amertil | Bahamas | 51.25 | Q, SB
|
| 11 | 3 | Kapachinskaya, AnastasiaAnastasia Kapachinskaya | Russia | 51.32 | Q
|
| 12 | 1 | Odumosu, AjokeAjoke Odumosu | Nigeria | 51.39 | Q, PB
|
| 13 | 1 | Trotter, DeedeeDeedee Trotter | United States | 51.41 | q
|
| 14 | 5 | Abugan, FolashadeFolashade Abugan | Nigeria | 51.45 | Q
|
| 15 | 3 | Wineberg, MaryMary Wineberg | United States | 51.46 | Q
|
| 16 | 6 | Williams, NovleneNovlene Williams | Jamaica | 51.52 | Q
|
| 17 | 2 | Muir, CarlineCarline Muir | Canada | 51.55 | Q, PB
|
| 18 | 2 | Terrero, IndiraIndira Terrero | Cuba | 51.56 | q
|
| 19 | 7 | Nachula, RachaelRachael Nachula | Zambia | 50.62 | Q
|
| 20 | 6 | Sanders, NicolaNicola Sanders | Great Britain | 51.81 | Q
|
| 21 | 3 | McConnell, LeeLee McConnell | Great Britain | 51.87 | Q
|
| 22 | 4 | Medina, GabrielaGabriela Medina | Mexico | 51.96 | Q
|
| 23 | 7 | Eze, Joy AmechiJoy Amechi Eze | Nigeria | 51.97 | q
|
| 24 | 2 | Bulikiobo Batimala, MakelesiMakelesi Bulikiobo Batimala | Fiji | 52.24 | SB
|
| 25 | 4 | Lewis, TamsynTamsyn Lewis | Australia | 52.38 |
|
| 26 | 7 | Kallinikou, AlissaAlissa Kallinikou | Cyprus | 52.40 |
|
| 27 | 1 | Ponteen, TiandraTiandra Ponteen | Saint Kitts and Nevis | 52.41 |
|
| 28 | 5 | Tanno, AsamiAsami Tanno | Japan | 52.60 |
|
| 29 | 5 | Ntova, DimitraDimitra Ntova | Greece | 52.69 |
|
| 30 | 6 | Eljack, NwalNwal Eljack | Sudan | 52.77 | Q
|
| 31 | 7 | Bejnar, MonikaMonika Bejnar | Poland | 52.80 |
|
| 32 | 6 | Alexander, KinekeKineke Alexander | Saint Vincent and the Grenadines | 52.87 |
|
| 33 | 2 | Kaur, MandeepMandeep Kaur | India | 52.88 |
|
| 33 | 6 | Batholomew, TrishTrish Batholomew | Grenada | 52.88 |
|
| 35 | 3 | Petrahn, BarbaraBarbara Petrahn | Hungary | 53.06 |
|
| 36 | 3 | Rodriguez, CarolCarol Rodriguez | Puerto Rico | 53.08 |
|
| 37 | 1 | Yefremova, AntoninaAntonina Yefremova | Ukraine | 53.22 |
|
| 38 | 4 | Almirao, Maria LauraMaria Laura Almirao | Brazil | 53.26 |
|
| 39 | 4 | Cuddihy, JoanneJoanne Cuddihy | Ireland | 53.32 |
|
| 40 | 5 | Tereshkova, OlgaOlga Tereshkova | Kazakhstan | 53.36 |
|
| 41 | 3 | Etienne, GinouGinou Etienne | Haiti | 53.94 |
|
| 42 | 5 | Davis, KiaKia Davis | Liberia | 53.99 |
|
| 43 | 6 | Thipe, TsholofeloTsholofelo Thipe | South Africa | 54.11 |
|
| 44 | 2 | Bayigga, JustineJustine Bayigga | Uganda | 54.15 |
|
| 45 | 7 | Thiebaud-Kangni, SandrineSandrine Thiebaud-Kangni | Togo | 54.16 |
|
| 46 | 6 | Shala, KlodianaKlodiana Shala | Albania | 54.84 |
|
| 47 | 6 | Batgerel, MunguntuyaMunguntuya Batgerel | Mongolia | 58.14 |
|
| 48 | 7 | Dlamini, TemalangeniTemalangeni Dlamini | Swaziland | 59.91 |
|
| 49 | 3 | Seini Maikidou, RachidatouRachidatou Seini Maikidou | Niger | 63.19 1:03.19 | NR
|
| 50 | 4 | Ali, GhadaGhada Ali | Libya | 66.19 1:06.19 |
|