1st(1st leg) RC Celta B - Marbella FC 2:0 (2:0)
2nd (2nd leg) Marbella FC - RC Celta B 4:5 (0:0, 2:0, 2:0) pso
1st(1st leg): 20/05/2018 11:00 2nd (2nd leg): 27/05/2018 11:00 Winner: RC Celta B
1st(1st leg) UE Cornellà - Sporting Gijón B 2:2 (1:0)
2nd (2nd leg) Sporting Gijón B - UE Cornellà 2:0 (1:0)
1st(1st leg): 20/05/2018 11:00 2nd (2nd leg): 26/05/2018 17:00 Winner: Sporting Gijón B
1st(1st leg) CF Fuenlabrada - Real Sociedad B 0:0 (0:0)
2nd (2nd leg) Real Sociedad B - CF Fuenlabrada 1:1 (0:0, 0:0) aet
1st(1st leg): 20/05/2018 11:00 2nd (2nd leg): 26/05/2018 16:00 Winner: CF Fuenlabrada
1st(1st leg) Athletic Club B - Villarreal CF B 1:3 (0:1)
2nd (2nd leg) Villarreal CF B - Athletic Club B 0:2 (0:2)
1st(1st leg): 20/05/2018 17:30 2nd (2nd leg): 26/05/2018 17:50 Winner: Villarreal CF B
1st(1st leg) Real Murcia - Elche CF 0:1 (0:0)
2nd (2nd leg) Elche CF - Real Murcia 3:2 (2:1)
1st(1st leg): 20/05/2018 17:30 2nd (2nd leg): 26/05/2018 16:30 Winner: Elche CF
1st(1st leg) Extremadura UD - Deportivo Fabril 2:1 (2:1)
2nd (2nd leg) Deportivo Fabril - Extremadura UD 3:2 (2:1, 2:1) aet
1st(1st leg): 20/05/2018 19:00 2nd (2nd leg): 26/05/2018 16:00 Winner: Extremadura UD