Runners-up Newry City won 6–3 on aggregate in the promotion play-off against Carrick Rangers, also achieving promotion to the Premiership for this season and relegating Carrick Rangers to the Championship.
The bottom team from the previous season, Lurgan Celtic, were relegated to the third-tier NIFL Premier Intermediate League.
The eleventh-placed team from the previous season, Dergview, remained in the Championship this season, after defeating the NIFL Premier Intermediate League runners-up Queen's University 4–1 on aggregate in the relegation play-off.
See: 2018–19 NIFL Premiership The eleventh-placed team from the Championship, PSNI, faced Annagh United, the runners-up from the 2018–19 Premier Intermediate League over two legs for one spot in the 2019–20 NIFL Championship.
PSNI won 5–3 on aggregate and retained their Championship status for the 2019–20 season.