| Regimental number | 15590 |
| Occupation | Public servant |
| Next of kin | Brother, Martin J O'Brien, c/o J W White, Solicitor, Timaru |
| Rank on embarkation | Private |
| Unit name | New Zealand Expeditionary Force, 15th Reinforcements (1st Draft), Canterbury Infantry Battalion, C Company |
| Embarkation details | Unit embarked from Wellington on board Waitemata on |
| Sources | Nominal Roll Vol. 2: Roll 37, p. 9 |