The 2004 Tercera División play-offs to Segunda División B from Tercera División (Promotion play-offs) were the final playoffs for the promotion from 2003–04 Tercera División to 2004–05 Segunda División B. The first four teams in each group (excluding reserve teams) took part in the competition.
Promotion to Segunda División B
Groups A
Teams from Galicia, Asturias, Castile and Leon and Madrid.
Group A1
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Navalcarnero
Group A2
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Atlético Arteixo
Group A3
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Marino de Luanco
Group A4
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Guijuelo
Groups B
Teams from Cantabria, Basque Country, La Rioja/Navarre and Aragon.
Group B1
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Huesca
Group B2
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Sestao River Club
Group B3
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Peralta
Group B4
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Lemona
Groups C
Teams from Catalonia, Valencian Community, Balearic Islands and Region of Murcia.
Group C1
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Badalona
Group C2
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Benidorm
Group C3
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Levante B
Group C4
1st Eliminatory:
2nd Eliminatory:
Promoted to Segunda División B:Alcoyano
Groups D
Teams from Andalusia, Extremadura, and Castile-La Mancha.
Group D1
1st Eliminatory: