The Women's 4x100m medley relay event at the 2010 South American Games was held on March 29 at 18:30.
| Standing records prior to the 2010 South American Games | ||||
|---|---|---|---|---|
| World record |  China | 3:52.19 | Rome, Italy | 1 August 2009 |
| Competition Record |  Venezuela | 4:18.47 | Buenos Aires, Argentina | 18 November 2006 |
| South American record |  Brazil | 3:58.49 | Rome, Italy | 1 August 2009 |
| Rank | Lane | Athlete | Result | Notes |
|---|---|---|---|---|
 | 4 | Brazil | 4:13.97 | CR |
| Fabíola Molina | 1:03.52 | |||
| Tatiane Sakemi | 1:13.33 | |||
| Daynara de Paula | 1:00.54 | |||
| Tatiana Barbosa | 56.58 | |||
 | 3 |  Argentina | 4:18.10 | |
| Cecilia Bertoncello | 1:07.28 | |||
| Agustina de Giovanni | 1:10.12 | |||
| Georgina Bardach | 1:02.97 | |||
| Nadia Colovini | 57.73 | |||
 | 6 |  Colombia | 4:20.53 | |
| Carolina Colorado Henao | 1:03.51 | |||
| Monica Álvarez | 1:14.68 | |||
| María Clara Sosa | 1:03.72 | |||
| Erika Stewart | 58.62 | |||
| 4 | 5 | Venezuela | 4:24.23 | |
| Jeserik Pinto | 1:06.56 | |||
| Daniela Victoria | 1:15.66 | |||
| Elimar Barrios | 1:03.94 | |||
| Arlene Semeco | 58.07 | |||
| 5 | 7 |  Peru | 4:32.95 | |
| Massie Milagros Yong | 1:07.53 | |||
| Patricia Mariana San Martin | 1:18.52 | |||
| Maria Graciela Rosales | 1:06.81 | |||
| Maria Alejandra Perez | 1:00.09 | |||
| 6 | 2 |  Ecuador | 4:36.83 | |
| Diana An Yu Ibarra | 1:06.71 | |||
| Camila Isabel Espinosa | 1:19.56 | |||
| Yamilé Bahamonde | 1:08.06 | |||
| Nicole Maria Gilbert | 1:02.50 | |||
| 7 | 1 |  Uruguay | 4:42.44 | |
| Ines Remersaro | 1:018.36 | |||
| Antonella Scanavino | 1:20.17 | |||
| Raissa Andrea Guerra | 1:08.50 | |||
| Maria Sanchez | 1:05.41 | |||
| 8 | 8 |  Paraguay | 4:47.78 | |
| Maria Laura Britez | 1:08.78 | |||
| Lujan Vargas | 1:21.88 | |||
| Silvana Valenzuela | 1:13.20 | |||
| Maria Nery Huerta | 1:03.92 | |||