| Regimental number | 3874 |
| Place of birth | Darlinghurst, Sydney, New South Wales |
| School | Christian Brothers (Catholic) College, Darlinghurst, New South Wales |
| Religion | Roman Catholic |
| Occupation | Engineer |
| Address | Darlinghurst, New South Wales |
| Marital status | Single |
| Age at embarkation | 18 |
| Next of kin | Father, A E O'Brien, 80 Barcom Avenue, Darlinghurst, New South Wales |
| Previous military service | Served as a Navy Cadet with the Naval Brigade, Rushcutters Bay, Sydney, NSW. |
| Enlistment date | |
| Rank on enlistment | Private |
| Unit name | 13th Battalion, 12th Reinforcement |
| AWM Embarkation Roll number | 23/30/3 |
| Embarkation details | Unit embarked from Sydney, New South Wales, on board HMAT A29 Suevic on |
| Rank from Nominal Roll | Gunner |
| Unit from Nominal Roll | 4th ATM Battery |
| Other details from Roll of Honour Circular | Died at the No.2 Casualty Clearing Station and was buried in the military cemetery at Outtersbeen, near Bailleul. |
| Fate | Died of wounds |
| Age at death | 18.10 |
| Age at death from cemetery records | 20 |
| Place of burial | Outtersteene Communal Cemetery Extension (Plot II, Row D, Grave No. 51), Bailleul, France |
| Panel number, Roll of Honour, Australian War Memorial | 20 |
| Miscellaneous information from cemetery records | Parents: Alfred Edward and Ellen Mary O'BRIEN, 80 Barcom Avenue, Darlinghurst, Sydney, New South Wales |
| Other details |
War service: Western Front Medals: British War Medal, Victory Medal |