| 1989–90 Cuban National Series | |
| League: | Cuban National Series |
| Sport: | Baseball |
| No Of Games: | 48 |
| No Of Teams: | 18 |
| Season: | Eastern zone |
| Season Champ Name: | Best record |
| Season Champs: | Santiago de Cuba (36–12) |
| Season2: | Western zone |
| Season Champ2 Name: | Best record |
| Season Champs2: | Henequeneros (37–11) |
| Playoffs: | Postseason |
| Finals Champ: | Henequeneros |
| Finals Runner-Up: | Santiago de Cuba |
| Seasonslistnames: | SNB |
| Prevseason Link: | 1988–89 Cuban National Series |
| Prevseason Year: | 1988–89 |
| Nextseason Link: | 1990–91 Cuban National Series |
| Nextseason Year: | 1990–91 |
In the 29th season of the Cuban National Series, the postseason format was changed. The league directly matched its two division winners in a best-of-seven series for the league championship, while the two division runners-up played a best-of-five series for third place. A four-team round-robin tournament had previously been used, since the 1985–86 season. The 18 teams of the league, and the regular-season schedule of 48 games, remained unchanged.
Henequeneros of Matanzas Province defeated Santiago de Cuba, four games to two, for the championship. Third place was won by Industriales over Granma.
| Team | W | L | Pct. | GB | |
|---|---|---|---|---|---|
| Henequeneros (Matanzas) | 37 | 11 | .770 | - | |
| Industriales (Havana) | 33 | 15 | .600 | 4 | |
| Vegueros (Pinar del Río) | 33 | 15 | .600 | 4 | |
| Metropolitanos (Havana) | 31 | 17 | .645 | 6 | |
| 27 | 21 | .500 | 10 | ||
| 18 | 30 | .375 | 19 | ||
| Citricultores (Matanzas) | 15 | 33 | .300 | 22 | |
| 14 | 34 | .291 | 23 | ||
| Forestales (Pinar del Río) | 8 | 40 | .166 | 29 |
| Team | W | L | Pct. | GB | |
|---|---|---|---|---|---|
| 36 | 12 | .750 | - | ||
| 28 | 20 | .583 | 8 | ||
| 26 | 22 | .541 | 10 | ||
| 26 | 22 | .541 | 10 | ||
| 25 | 23 | .520 | 11 | ||
| 24 | 24 | .500 | 12 | ||
| 18 | 30 | .375 | 18 | ||
| 17 | 31 | .354 | 19 | ||
| 16 | 32 | .333 | 20 |