1 Battalion: Unit strength on 11 July 1921 was 359 all ranks, and the strength on 1 July 1922 was 265 all ranks. (Note: this unit was designated as the 2 Battalion for the period 11 July 1921.)The companies of the 1 Battalion were located as follows:  Coosan,  Mount Temple,  Kiltoom,  Athlone,  Moate,  Faheran,  and Monksland.
2 Battalion: Unit strength on 11 July 1921 was 184 all ranks, and the strength on 1 July 1922 was 164 all ranks. (Note: this unit was designated as the 1st Battalion for the period 11 July 1921). The companies of the 2 Battalion were located as follows:  Drumraney,  Tang,  Tubberclair,  Ballymore,  Bishopstown,  Rosemount,  and Moyvore.
3 Battalion (Summerhill): Unit strength on 11 July 1921 was 347 all ranks. This unit (less ‘G’ Coy. which transferred to the 1 Bn. Athlone Brigade) was transferred to the 2 Western Division on 1 July 1922 and was designated as the 5 Battalion, 3 Brigade, 2 Western Division. On the 11 July 1921 the companies of the 3 Battalion were located as follows: Summerhill, Drum, Bealnamulla, Clonown, Taughmaconnell, Moone and Monksland.

An Active Service Unit was effective with the Athlone Brigade up to 1 July 1922 with a total overall strength of 64 all ranks. Personnel were attached to the A.S.U from the battalions of the brigade.