18 teams from the states of Bremen, Hamburg, Lower Saxony and Schleswig-Holstein competed in the sixth season of the reformed Regionalliga Nord; 15 teams were retained from last season and 3 were promoted from the Oberliga, namely 2016–17 Niedersachsenliga champions SSV Jeddeloh and promotion round winners Eutin 08, 2016–17 Schleswig-Holstein-Liga champions, and Altona 93, 2016–17 Oberliga Hamburg champions.
A play-off was held between the two leagues' runners-up, Optik Rathenow and Germania Halberstadt, to determine the last participant.
As the Westphalian Football and Athletics Association is one of three regional associations with the most participating teams in their league competitions, they were allowed to enter a second team for the 2018–19 DFB-Pokal (in addition to the Westphalian Cup winners).
A play-off took place between the best-placed eligible (non-reserve) Westphalian team of the Regionalliga West, SV Rödinghausen, and the best-placed eligible team of the Oberliga Westfalen, SV Lippstadt, with the winners qualifying for the DFB-Pokal.
19 teams from Baden-Württemberg, Hesse, Rhineland-Palatinate and Saarland competed in the sixth season of the Regionalliga Südwest; 13 teams were retained from last season and 4 were promoted from the Oberliga.
The runners-up of the other Oberligas had a play-off round which was won by Röchling Völklingen.
Finally, in a play-off between the two losing teams, Greuther Fürth II beat Viktoria Aschaffenburg, obtaining the last open spot in the league.