| Regimental number | 3458 |
| Place of birth | Drillham, Queensland |
| Religion | Roman Catholic |
| Occupation | Farmer |
| Address | Bell, Queensland |
| Marital status | Single |
| Age at embarkation | 27 |
| Height | 5' 9" |
| Weight | 190 lbs |
| Next of kin | Father, Hugh O'Brien, Bell, Queensland |
| Previous military service | Served in the Light Horse, Bell; time expired. |
| Enlistment date | |
| Place of enlistment | Dalby, Queensland |
| Rank on enlistment | Private |
| Unit name | 41st Battalion, 8th Reinforcement |
| AWM Embarkation Roll number | 23/58/3 |
| Embarkation details | Unit embarked from Sydney, New South Wales, on board HMAT A20 Hororata on |
| Regimental number from Nominal Roll | 3458 |
| Rank from Nominal Roll | Private |
| Unit from Nominal Roll | 41st Battalion |
| Fate | Returned to Australia |
| Discharge date | |
| Other details |
War service: Western Front Commenced return to Australia on board HT 'Ajana', 19 August 1919; discharged (termination of period of enliastment), Brisbane, 10 November 1919. Medals: British War Medal, Victory Medal |
| Miscellaneous details | Service number entered as 3434 on Embarkation Roll. |
| Sources | NAA: B2455, O'BRIEN Patrick Francis Hugh |