See main article: Swimming at the 2010 South American Games. The Women's 400m freestyle event at the 2010 South American Games was held on March 26, with the heats at 10:23 and the Final at 18:11.
| width=200 bgcolor=gold | Gold | width=200 bgcolor=silver | Silver | width=200 bgcolor=CC9966 | Bronze |
| Joanna Maranhão | Kristel Kobrich | Cecilia Biagioli |
| Standing records prior to the 2010 South American Games | |||||
|---|---|---|---|---|---|
| World record | 3:59.15 | Rome, Italy | 26 July 2009 | ||
| Competition Record | 4:13.63 | Buenos Aires, Argentina | 15 November 2006 | ||
| South American record | 4:10.16 | Rome, Italy | 26 July 2009 | ||
| Rank | Heat | Lane | width=250 | Athlete ! | width=100 | Result ! | Notes |
|---|---|---|---|---|---|---|---|
| 1 | 2 | 5 | 4:26.78 | Q | |||
| 2 | 1 | 5 | 4:27.50 | Q | |||
| 3 | 1 | 4 | 4:27.59 | Q | |||
| 4 | 2 | 3 | 4:28.57 | Q | |||
| 5 | 1 | 3 | 4:30.32 | Q | |||
| 6 | 1 | 6 | 4:30.92 | Q | |||
| 7 | 2 | 6 | 4:30.99 | Q | |||
| 8 | 2 | 2 | 4:31.70 | Q | |||
| 9 | 2 | 1 | 4:33.14 | ||||
| 10 | 2 | 7 | 4:34.54 | ||||
| 11 | 1 | 7 | 4:35.08 | ||||
| 12 | 1 | 1 | 4:38.48 | ||||
| 13 | 1 | 2 | 4:47.13 | ||||
| 14 | 2 | 4 | 4:52.23 | ||||
| 2 | 8 | DNS | |||||
| Rank | Lane | width=250 | Athlete ! | width=100 | Result ! | Notes |
|---|---|---|---|---|---|---|
| 5 | 4:13.79 | |||||
| 4 | 4:15.26 | |||||
| 3 | 4:15.55 | |||||
| 4 | 6 | 4:27.94 | ||||
| 5 | 1 | 4:29.46 | ||||
| 6 | 8 | 4:31.83 | ||||
| 7 | 7 | 4:34.13 | ||||
| 8 | 2 | 4:37.96 | ||||