| Regimental number | 10/1938 |
| Date of birth | |
| Place of birth | Kaiapoi Island |
| Religion | No religious affiliation stated |
| Occupation | Labourer |
| Address | Raetihi, Waimarino |
| Marital status | Single |
| Age at embarkation | 31 |
| Height | 5' 7.5" |
| Weight | 140 lbs |
| Next of kin | Father, Denis O'Callaghan, Belfast, Canterbury |
| Previous military service | Nil |
| Enlistment date | |
| Place of enlistment | Trentham |
| Rank on embarkation | Private |
| Enlistment status | Volunteer |
| Unit name | New Zealand Expeditionary Force, 4th Reinforcements, Wellington Infantry Battalion |
| Embarkation details | Unit embarked from Wellington on |
| The 4th Reinforcements, Wellington Infantry Battalion, left New Zealand on board three ships (HMNZT 21 'Willochra', HMNZT 22 'Knight Templar', and HMNZT 23 'Waitomo'). It is not possible from the Nominal Roll to determine on which ship an individual embarked. | |
| Final rank | Private |
| Final unit | Wellington Infantry Regiment |
| Fate | Killed in Action |
| Place of burial | No known grave |
| Commemoration details | Chunuk Bair (New Zealand) Memorial (Panel No 22), Gallipoli, Turkey |
| Miscellaneous information from cemetery records | Parents: Mr & Mrs Denis O'Callaghan, 104 Nursery Road, Linwood, Christchurch |
| Other details |
War service: Egypt, Gallipoli Killed in action, 8 August 1915. War service: 215 days (of which 114 days were abroad) Medals: 1914-15 Star, British War Medal, Victory Medal |
| Miscellaneous details | Nominal Roll Vol. 1: Wellington Infantry Batln/Fourth |
| Sources | Archives New Zealand (Wellington), Agency AABK, Series 18805, File 21381498 |