| Competition: | Primera B Nacional |
| Season: | 2008–09 |
| Winners: | Atlético Tucumán (1st divisional title) |
| Promoted: | Atlético Tucumán Chacarita Juniors |
| Relegated: | Almagro Talleres (C) |
| League Topscorer: | Luis Rodriguez 20 goals |
| Matches: | 380 |
| Total Goals: | 898 |
| Prevseason: | 2007–08 |
| Nextseason: | 2009–10 |
The 2008–09 Argentine Primera B Nacional was the 23rd season of second division professional of football in Argentina. A total of 20 teams competed; the champion and runner-up were promoted to Argentine Primera División.
The 3rd and 4th placed of the table played with the 18th and the 17th placed of the Relegation Table of 2008–09 Primera División.|-!colspan="5"|Relegation/promotion playoff 1|-!colspan="5"|Relegation/promotion playoff 2
| width=28 | width=185 | Team | width=50 | width=50 | width=50 | width=50 | width=50 | width=50 | Situation | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Atlético Tucumán | — | — | 74 | 74 | 38 | Indirect | ||||||||||
| 2 | Chacarita Juniors | 61 | 56 | 72 | 189 | 114 | Direct | ||||||||||
| 3 | Atlético de Rafaela | 68 | 53 | 62 | 183 | 114 | Indirect | ||||||||||
| 4 | — | 56 | 62 | 118 | 76 | Indirect | |||||||||||
| 5 | Olimpo | 75 | — | 40 | 118 | 76 | Indirect | ||||||||||
| 6 | San Martín (SJ) | 69 | — | 49 | 118 | 76 | Indirect | ||||||||||
| 7 | Unión | 57 | 56 | 49 | 162 | 114 | Direct | ||||||||||
| 8 | Quilmes | — | 55 | 51 | 106 | 76 | Direct | ||||||||||
| 9 | Aldosivi | 45 | 48 | 57 | 150 | 114 | Indirect | ||||||||||
| 10 | All Boys | — | — | 50 | 50 | 38 | Direct | ||||||||||
| 11 | 57 | 43 | 49 | 149 | 114 | Direct | |||||||||||
| 12 | Independiente Rivadavia | — | 47 | 50 | 97 | 76 | Indirect | ||||||||||
| 13 | Instituto | 43 | 43 | 59 | 145 | 114 | Indirect | ||||||||||
| 14 | Tiro Federal | 39 | 54 | 50 | 143 | 114 | Indirect | ||||||||||
| 15 | Ferro Carril Oeste | 39 | 51 | 52 | 142 | 114 | Direct | ||||||||||
| 16 | Platense | 61 | 41 | 37 | 139 | 114 | Direct | ||||||||||
| 17 | Los Andes | — | — | 45 | 45 | 38 | Relegation Playoff Matches | Direct | |||||||||
| 18 | 45 | 51 | 36 | 132 | 114 | Relegation Playoff Matches | Indirect | ||||||||||
| 19 | Almagro | 49 | 43 | 32 | 124 | 114 | Primera B Metropolitana | Direct | |||||||||
| 20 | Talleres (C) | 26 | 46 | 50 | 122 | 114 | Torneo Argentino A | Indirect |
The bottom two teams of this table face relegation regardless of their affiliation status. Apart from them, the bottom teams of each affiliation face promotion/relegation playoffs against Torneo Argentino A and Primera B Metropolitana's "Reducido" (reduced tournaments) champions. The Reducidos are played after those leagues' champions are known.
|-!colspan="5"|Relegation/promotion playoff 1 (Direct affiliation vs. Primera B Metropolitana)|-!colspan="5"|Relegation/promotion playoff 2 (Indirect affiliation vs. Torneo Argentino A)|-|}
| Rank | Player | Club | Goals |
|---|---|---|---|
| 1 |  Luis Rodriguez | Atlético Tucumán | 20 |
| 2 | Luis Salmerón | Talleres (C) | 18 |
| 3 | Emanuel Gigliotti | All Boys | 16 |
| Javier Toledo | Chacarita Juniors | ||
| Juan José Morales | Quilmes | ||
| 6 | Matías Alustiza | Chacarita Juniors | 14 |
| Javier Rossi | Tiro Federal |