| Regimental number | 12397 |
| Religion | Roman Catholic |
| Occupation | Clerk |
| Address | G P O Melbourne, Melbourne, Victoria |
| Marital status | Single |
| Age at embarkation | 19 |
| Next of kin | Brother, A O'Brien, 36 Garfield Street, Launceston, Tasmania |
| Enlistment date | 16 November 1915 |
| Date of enlistment from Nominal Roll | 7 November 1915 |
| Rank on enlistment | Gunner |
| Unit name | Field Artillery Brigade 6, Reinforcement 3 |
| AWM Embarkation Roll number | 13/34/2 |
| Embarkation details | Unit embarked from Melbourne, Victoria, on board HMAT A32 Themistocles on 28 January 1916 |
| Rank from Nominal Roll | Driver |
| Unit from Nominal Roll | 4th Field Artillery Brigade |
| Fate | Returned to Australia 31 March 1919 |
| Miscellaneous details (Nominal Roll) | *Spelt Michael Morton O'Brien on NR |
