The championships between 1915 and 1918 do not count as official competitions - unlike in the state cup competition - and the respective winners have therefore not won an official title. The game was played from September 7th to November 16th 1918. The winner was Belfast Celtic
The six teams played against each other twice on a total of ten match days. Glenavon FC has been replaced by Belfast Celtic. The tied teams Belfast Celtic and Linfield FC determined the unofficial champions in a play-off game at the end of the season.