| Regimental number | 9957 |
| Religion | Roman Catholic |
| Occupation | Labourer |
| Address | Sebastopol Street, Marrickville, New South Wales |
| Marital status | Single |
| Age at embarkation | 21 |
| Next of kin | Father, Charles O'Neill, "Bethany", Sebastopol Street, Marrickville, New South Wales |
| Enlistment date | 13 October 1915 |
| Rank on enlistment | Gunner |
| Unit name | Field Artillery Brigade 1, Reinforcement 13 |
| AWM Embarkation Roll number | 13/29/3 |
| Embarkation details | Unit embarked from Sydney, New South Wales, on board HMAT A35 Berrima on 17 December 1915 |
| Rank from Nominal Roll | Gunner |
| Unit from Nominal Roll | 1st Field Artillery Brigade |
| Fate | Returned to Australia 20 April 1919 |
| Family/military connections | Brothers: 3369 Pte John Patrick O'NEIL, MM, 18th Bn, killed in action, 16 October 1917; 7367 Pte Frank Joseph O'NEILL, 13th Bn, returned to Australia, 6 July 1919; 1263 Pte Charles Bernard O'NEILL, 1st Light Horse Regiment, returned to Australia, 20 December 1918. |
