2019 IAAF World Relays – Mixed 4 × 400 metres relay

The mixed 4 × 400 metres relay at the 2019 IAAF World Relays was held at the Nissan Stadium on 11 and 12 May.

Records
Prior to the competition, the records were as follows:

Heats
Qualification: First 2 of each heat (Q) plus the 2 fastest times (q) advanced to the final.