The men's 400 metres event at the 2019 Summer Universiade was held on 8, 9 and 10 July at the Stadio San Paolo in Naples.
| width=200 bgcolor=gold | Gold | width=200 bgcolor=silver | Silver | width=200 bgcolor=CC9966 | Bronze |
| Valente Mendoza | Mikhail Litvin | Gardeo Isaacs |
Qualification: First 3 in each heat (Q) and next 3 fastest (q) qualified for the semifinals.[1]
| Rank | Heat | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | 5 | 46.39 | Q, SB | |||
| 1 | 6 | 46.39 | Q | |||
| 3 | 6 | 46.58 | Q, PB | |||
| 4 | 5 | 46.67 | Q | |||
| 5 | 4 | 46.77 | Q | |||
| 6 | 5 | 46.93 | Q | |||
| 7 | 4 | 46.94 | Q | |||
| 8 | 4 | 47.03 | Q | |||
| 9 | 2 | 47.03 | Q | |||
| 10 | 2 | 47.06 | Q | |||
| 11 | 4 | 47.07 | q, PB | |||
| 12 | 7 | 47.11 | Q | |||
| 13 | 5 | 47.14 | q | |||
| 14 | 3 | 47.24 | Q, PB | |||
| 15 | 3 | 47.25 | Q | |||
| 16 | 7 | 47.41 | Q | |||
| 17 | 3 | 47.45 | Q | |||
| 18 | 3 | 47.51 | q, PB | |||
| 19 | 1 | 47.55 | Q | |||
| 20 | 2 | 47.55 | Q | |||
| 21 | 1 | 47.81 | Q | |||
| 22 | 6 | 47.82 | Q | |||
| 23 | 7 | 47.83 | Q | |||
| 24 | 3 | 47.98 | ||||
| 25 | 1 | 48.06 | Q, SB | |||
| 26 | 7 | 48.14 | ||||
| 27 | 5 | 48.16 | ||||
| 28 | 6 | 48.18 | ||||
| 29 | 1 | 48.21 | ||||
| 30 | 1 | 48.22 | SB | |||
| 31 | 3 | 48.31 | ||||
| 32 | 1 | 48.37 | ||||
| 32 | 5 | 48.37 | SB | |||
| 34 | 1 | 48.73 | ||||
| 35 | 7 | 48.89 | ||||
| 36 | 4 | 49.21 | ||||
| 37 | 7 | 49.22 | ||||
| 38 | 7 | 49.29 | PB | |||
| 39 | 4 | 49.35 | SB | |||
| 40 | 2 | 49.46 | ||||
| 41 | 3 | 49.47 | ||||
| 42 | 4 | 49.50 | ||||
| 43 | 4 | 49.59 | ||||
| 44 | 6 | 49.59 | ||||
| 45 | 6 | 49.62 | ||||
| 46 | 6 | 49.85 | ||||
| 47 | 2 | 50.09 | ||||
| 48 | 2 | 50.20 | ||||
| 49 | 3 | 50.42 | ||||
| 50 | 1 | 50.46 | SB | |||
| 51 | 6 | 50.77 | ||||
| 52 | 2 | 51.03 | ||||
| 53 | 5 | 51.99 | PB | |||
| 54 | 5 | |||||
| 7 |
Qualification: First 2 in each heat (Q) and next 2 fastest (q) qualified for the final.[2]
| Rank | Heat | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | 3 | 45.75 | Q, PB | |||
| 2 | 2 | 45.84 | Q, SB | |||
| 3 | 1 | 46.02 | Q | |||
| 4 | 1 | 46.05 | Q | |||
| 5 | 3 | 46.09 | Q, PB | |||
| 6 | 1 | 46.31 | q | |||
| 7 | 1 | 46.40 | q, PB | |||
| 8 | 2 | 46.57 | Q | |||
| 9 | 2 | 46.59 | ||||
| 10 | 2 | 46.67 | ||||
| 11 | 3 | 46.77 | ||||
| 12 | 1 | 46.80 | SB | |||
| 13 | 3 | 46.86 | ||||
| 14 | 2 | 46.94 | PB | |||
| 15 | 3 | 47.16 | ||||
| 16 | 3 | 47.18 | ||||
| 17 | 2 | 47.26 | ||||
| 18 | 1 | 47.32 | ||||
| 19 | 3 | 47.38 | ||||
| 20 | 3 | 47.60 | ||||
| 21 | 2 | 47.60 | PB | |||
| 22 | 1 | 47.97 | SB | |||
| 23 | 2 | 48.09 | ||||
| 1 | 163.3a[3] |
| Rank | Lane | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 4 | 45.63 | PB | ||||
| 3 | 45.77 | SB | ||||
| 6 | 45.89 | PB | ||||
| 4 | 7 | 46.23 | ||||
| 5 | 1 | 46.36 | PB | |||
| 6 | 5 | 46.62 | ||||
| 7 | 2 | 46.64 | ||||
| 8 | 8 | 46.69 |