The men's 800 metres event at the 2000 World Junior Championships in Athletics was held in Santiago, Chile, at Estadio Nacional Julio Martínez Prádanos on 17, 18 and 20 October.
| Gold | Nicholas Wachira | |
| Silver | Florent Lacasse | |
| Bronze | Antonio Manuel Reina |
20 October
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| align=left | align=left | | 1:47.16 | ||||
| align=left | align=left | | 1:47.61 | ||||
| align=left | align=left | | 1:47.90 | ||||
| 4 | align=left | align=left |  | 1:48.51 | |||
| 5 | align=left | align=left | 1:49.10 | ||||
| 6 | align=left | align=left |  | 1:49.88 | |||
| 7 | align=left | align=left |  | 1:50.34 | |||
| 8 | align=left | align=left |  | 1:50.63 | |||
| 9 | align=left | align=left | | 1:50.92 |
18 October
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 1:48.13 | Q | ||
| 2 | align=left | align=left | | 1:48.30 | Q | ||
| 3 | align=left | align=left | | 1:48.44 | Q | ||
| 4 | align=left | align=left | 1:51.19 | ||||
| 5 | align=left | align=left | | 1:52.56 | q | ||
| 6 | align=left | align=left | 1:53.40 | ||||
| 7 | align=left | align=left | 1:54.52 | ||||
| 8 | align=left | align=left | | 3:00.54 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 1:49.06 | Q | ||
| 2 | align=left | align=left | 1:49.42 | Q | |||
| 3 | align=left | align=left | | 1:49.80 | Q | ||
| 4 | align=left | align=left | | 1:50.14 | q | ||
| 5 | align=left | align=left | | 1:50.27 | q | ||
| 6 | align=left | align=left | | 1:50.29 | |||
| 7 | align=left | align=left |  | 1:52.81 | |||
| 8 | align=left | align=left |  | 1:54.65 |
17 October
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 1:51.05 | Q | ||
| 2 | align=left | align=left | | 1:51.39 | Q | ||
| 3 | align=left | align=left | | 1:51.43 | Q | ||
| 4 | align=left | align=left | | 1:51.55 | q | ||
| 5 | align=left | align=left | | 1:51.65 | |||
| 6 | align=left | align=left | 1:51.69 | ||||
| 7 | align=left | align=left |  | 1:56.80 | |||
| 8 | align=left | align=left | 2:02.72 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | 1:49.81 | Q | |||
| 2 | align=left | align=left | | 1:50.15 | Q | ||
| 3 | align=left | align=left | | 1:50.36 | Q | ||
| 4 | align=left | align=left | | 1:50.80 | q | ||
| 5 | align=left | align=left | 1:51.43 | q | |||
| 6 | align=left | align=left | 1:51.95 | ||||
| 7 | align=left | align=left | 1:53.14 | ||||
| 8 | align=left | align=left | 1:57.98 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 1:50.91 | Q | ||
| 2 | align=left | align=left | | 1:51.13 | Q | ||
| 3 | align=left | align=left | 1:52.21 | Q | |||
| 4 | align=left | align=left | 1:56.01 | ||||
| 5 | align=left | align=left | 1:56.93 | ||||
| 6 | align=left | align=left | 1:59.68 |
| Rank | Name | Nationality | Time | Notes | |||
|---|---|---|---|---|---|---|---|
| 1 | align=left | align=left | | 1:50.84 | Q | ||
| 2 | align=left | align=left | | 1:51.15 | Q | ||
| 3 | align=left | align=left | 1:51.45 | Q | |||
| 4 | align=left | align=left | | 1:51.57 | q | ||
| 5 | align=left | align=left |  | 1:52.48 | |||
| 6 | align=left | align=left | 2:00.73 | ||||
| 7 | align=left | align=left | 2:04.40 |
According to an unofficial count, 29 athletes from 24 countries participated in the event.