The battalion was composed of volunteers from militia units in central Ontario. Much of the unit was drawn from the 12th York Regiment, the Rangers, with men coming from ten other militia regiments of which four still exist.
The unit fought in France and Flanders as part of the 4th Canadian Brigade, 2nd Canadian Division.
Notable actions include the Somme, Vimy Ridge, Hill 70, Passchendaele, Amiens, the advance along the Scarpe, Canal du Nord, Canal de le Escault and the advance to Mons in the Last Hundred Days.
The battalion was disbanded in 1920.
The 20th Battalion was awarded the following battle honours:
Mount Sorrel
Somme 1916, 1918
Flers-Courcelette
Thiepval
Ancre Heights
Arras 1917, 1918
Vimy 1917
Arleux
Scarpe 1917, 1918
Hill 70
Ypres 1917
Passchendaele
Amiens
Hindenburg Line
Canal du Nord
Cambrai 1918
Pursuit to Mons
France and Flanders 1915, 1918
Numeral Collar Badge
Formation Patche
Cap Badge
Benett, John Thomas #139020
Hides, Alfred Harry #405294
Rattier, Antoine #57486