| Event: | Mixed 4 × 400 metres relay |
| Competition: | 2019 IAAF World Relays |
| Venue: | Nissan Stadium |
| Dates: | 11 May (heats) & 12 May (finals A&B) |
| Nations: | 17 |
| Win Value: | 3:16.43 |
| Gold: | My'Lik Kerley Joanna Atkins Jasmine Blocker Dontavius Wright Brionna Thomas |
| Goldnoc: | USA |
| Silver: | Austin Cole Aiyanna Stiverne Zoe Sherar Philip Osei Alicia Brown |
| Silvernoc: | CAN |
| Bronze: | Jared Momanyi Maureen Thomas Hellen Syombua Aron Koech |
| Bronzenoc: | KEN |
| Prev: | 2017 |
| Next: | 2021 |
The mixed 4 × 400 metres relay at the 2019 IAAF World Relays was held at the Nissan Stadium on 11 and 12 May.
Prior to the competition, the records were as follows:
| World record |  United States | 3:13.20 | Eugene, United States | 29 July 2016 | |
| Championship record |  Bahamas | 3:14.42 | Nassau, Bahamas | 23 April 2017 |
| KEY: | bgcolor=ccffcc align=center | Q | Qualified | bgcolor=ddffdd align=center | q | Fastest non-qualifiers | WL | World leading | CR | Championship record | NR | National record | SB | Seasonal best | WC | 2019 World Championships qualification |
Qualification: First 2 of each heat (Q) plus the 2 fastest times (q) advanced to the final.[1] [2]
| Rank | Heat | Nation | Athletes | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | 3 | Kajetan Duszyński (M), Patrycja Wyciszkiewicz (W), Justyna Święty-Ersetic (W), Karol Zalewski (M) | 3:15.46 | Q, WL, AR, *WC | ||
| 2 | 3 | Brionna Thomas (W), My'Lik Kerley (M), Olivia Baker (W), Dontavius Wright (M) | 3:16.01 | Q, SB, *WC | ||
| 3 | 3 | Davide Re (M), Giancarla Trevisan (W), Andrew Howe (M), Raphaela Lukudo (W) | 3:16.12 | q, NR*,[3] *WC | ||
| 4 | 2 | Austin Cole (M), Aiyanna Stiverne (W), Alicia Brown (W), Philip Osei (M) | 3:16.78 | Q, NR, *WC | ||
| 5 | 2 | Tobias Lange (M), Laura Müller (W), Nadine Gonska (W), Torben Junker (M) | 3:16.85 | Q, NR, *WC | ||
| 6 | 2 | Jared Nyambweke Momanyi (M), Maureen Nyatichi Thomas (W), Hellen Syombua (W), Aron Koech (M) | 3:16.90 | q, NR, *WC | ||
| 7 | 1 | Julien Watrin (M), Camille Laus (W), Liefde Schoemaker (W), Dylan Borlée (M) | 3:18.03 | Q, NR, *WC | ||
| 8 | 1 | Lucas Carvalho (M), Tiffani Marinho (W), Cristiane Silva (W), Alexander Russo (M) | 3:18.26 | Q, AR, *WC | ||
| 9 | 1 | Fitzroy Dunkley (M), Janieve Russell (W), Rhonda Whyte (W), Jamari Rose (M) | 3:18.47 | NR, *WC | ||
| 10 | 3 | Wilfried Happio (M), Kellya Pauline (W), Estelle Perrossier (W), Nicolas Courbiere (M) | 3:18.93 | NR, *WC | ||
| 11 | 3 | Rikuya Ito (M), Seika Aoyama (W), Mayu Inaoka (W), Naoki Kitadani (M) | 3:19.71 | NR, *WC | ||
| 12 | 2 | Alex Haydock-Wilson (M), Finette Agyapong (W), Anyika Onuora (W), Jamal Rhoden-Stevens (M) | 3:20.49 | NR, *WC | ||
| 13 | 2 | Lu Zhiquan (M), Wang Chunyu (W), Huang Guifen (W), Yu Yang (M) | 3:21.66 | |||
| 14 | 1 | Ian Halpin (M), Rebecca Bennett (W), Angeline Blackburn (W), Luke Stevens (M) | 3:21.80 | SB | ||
| 15 | 1 | Jithu Baby (M), Sonia Baishya (W), Prachi (W), Antony Alex (M) | 3:23.59 | |||
| 16 | 2 | Andrey Sokolov (M), Svetlana Golendova (W), Elina Mikhina (W), Mikhail Litvin (M) | 3:24.54 | |||
| 3 | Emmanuel Wanga (M), Leonie Beu (W), Shadrick Tansi (M), Isila Manukip Apkup (W) | R170.19[4] | ||||
| 1 |
| Rank | Nation | Athletes | Time | Notes | Points | |
|---|---|---|---|---|---|---|
| My'Lik Kerley (M), Joanna Atkins (W), Jasmine Blocker (W), Dontavius Wright (M) | 3:16.43 | 8 | ||||
| Austin Cole (M), Aiyanna Stiverne (W), Zoe Sherar (W), Philip Osei (M) | 3:18.15 | 7 | ||||
| Jared Momanyi (M), Maureen Thomas (W), Hellen Syombua (W), Aron Koech (M) | 3:19.43 | 6 | ||||
| 4 | Giuseppe Leonardi (M), Virginia Troiani (W), Chiara Bazzoni (W), Alessandro Sibilio (M) | 3:20.28 | 5 | |||
| 5 | Przemysław Waściński (M), Małgorzata Hołub-Kowalik (W), Justyna Saganiak (W), Patryk Dobek (M) | 3:20.65 | 4 | |||
| 6 | Lucas Carvalho (M), Tiffani Marinho (W), Cristiane Silva (W), Alexander Russo (M) | 3:20.71 | 3 | |||
| 7 | Marc Koch (M), Corinna Schwab (W), Svea Köhrbrück (W), Marvin Schlegel (M) | 3:22.26 | 2 | |||
| 8 | Julien Watrin (M), Lucie Ferauge (W), Hanne Claes (W), Jonathan Sacoor (M) | 3:25.74 | 1 |