The Women's 400 metres at the 2011 All-Africa Games took place on 11–13 September at the Estádio Nacional do Zimpeto.
The final held at 5:45 p.m. local time.
Prior to the competition, the records were as follows:
Qualification: First 3 in each heat (Q) and the next 4 fastest (q) advance to the semifinals.
Qualification: First 3 in each heat (Q) and the next 2 fastest (q) advance to the final.