The women's 4 × 400 metres relay at the 2015 IAAF World Relays was held at the Thomas Robinson Stadium on 2–3 May.

Prior to the competition, the records were as follows: All times are local times (UTC−4) Qualification: First 2 of each heat (Q) plus the 2 fastest times (q) advanced to the final.

[1][2] The final B was started at 20:20.

[3] The final was started at 20:32.

[4]