The girls' 400 metre freestyle event at the 2010 Youth Olympic Games took place on August 20 at the Singapore Sports School.
| 4:10.37 | ||
| 4:14.28 | ||
| 4:14.31 |
| Rank | Lane | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | 3 | Nesrine Khelifati | 4:37.37 | |||
| 2 | 4 | Saskia Postma | 4:41.63 | |||
| 3 | 5 | Karlene van der Jagt | 4:45.03 |
| Rank | Lane | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | 4 | Stefania Pirozzi | 4.18.36 | Q | ||
| 1 | 5 | Kiera Janzen | 4.18.36 | Q | ||
| 3 | 3 | Annick van Westendorp | 4:20.17 | |||
| 4 | 2 | Simona Marinova | 4:25.31 | |||
| 5 | 7 | Andrea Cedron | 4:27.26 | |||
| 6 | 6 | Shahd Mostafa | 4:27.48 | |||
| 7 | 8 | Kaori Miyahara | 4:29.27 | |||
| 8 | 1 | Marija Joksimović | 4:32.25 |
| Rank | Lane | Name | Nationality | Time | Notes |
|---|---|---|---|---|---|
| 1 | 4 | Eleanor Faulkner | 4:14.75 | Q | |
| 2 | 5 | Jordan Mattern | 4:19.51 | Q | |
| 3 | 3 | Anna Olasz | 4:19.71 | Q | |
| 4 | 7 | Inga Elin Cryer | 4:28.68 | ||
| 5 | 1 | Wei Li Lai | 4:30.92 | ||
| 6 | 6 | Natasha de Vos | 4:33.68 | ||
| 7 | 8 | Shannon Austin | 4:34.81 | ||
| 8 | 2 | Emma McKeon | DNS | ||
| Rank | Lane | Name | Nationality | Time | Notes |
|---|---|---|---|---|---|
| 1 | 4 | Boglárka Kapás | 4:16.02 | Q | |
| 2 | 3 | Claudia Dasca | 4:18.02 | Q | |
| 3 | 7 | Julia Hassler | 4:18.59 | Q | |
| 4 | 5 | Chloe Francis | 4:22.59 | ||
| 5 | 6 | Julia Gerotto | 4:23.71 | ||
| 6 | 2 | Lauren Earp | 4:26.47 | ||
| 7 | 8 | Jurate Scerbinskaite | 4:33.08 | ||
| 8 | 1 | Chriselle Koh | 4:34.28 | ||
| Rank | Lane | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 5 | Boglárka Kapás | 4:10.37 | ||||
| 2 | Kiera Janzen | 4:14.28 | ||||
| 4 | Eleanor Faulkner | 4:14.31 | ||||
| 4 | 6 | Stefanie Pirozzi | 4:14.61 | |||
| 5 | 3 | Claudia Dasca | 4:14.81 | |||
| 6 | 1 | Jordan Mattern | 4:14.94 | |||
| 7 | 7 | Julia Hassler | 4:17.25 | |||
| 8 | 8 | Anna Olasz | 4:20.24 |