| Regimental number | 542 |
| Place of birth | Ross, Westland, New Zealand |
| School | Westport High School, Westport, New Zealand |
| Religion | Church of England |
| Occupation | Loco.employee |
| Address | corner of Hare and Parsons Streets, Kalgoorlie, Western Australia |
| Marital status | Single |
| Age at embarkation | 23 |
| Next of kin | Father, James P. Hallahan, Weston's Find, Carabbin, Western Australia |
| Enlistment date | |
| Rank on enlistment | Private |
| Unit name | 11th Battalion, E Company |
| AWM Embarkation Roll number | 23/28/1 |
| Embarkation details | Unit embarked from Fremantle, Western Australia, on board HMAT A11 Ascanius on |
| Rank from Nominal Roll | Corporal |
| Unit from Nominal Roll | 51st Battalion |
| Other details from Roll of Honour Circular | "One of four brothers who were in the Gallipoli landing. Two others were killed in France". Details from Father. |
| Fate | Killed in Action |
| Place of death or wounding | Amiens, France |
| Age at death | 26 |
| Age at death from cemetery records | 24 |
| Place of burial | Rue-Du-Bois Military Cemetery (Plot I, Row C, Grave No. 14), Fleurbaix, France |
| Panel number, Roll of Honour, Australian War Memorial | 152 |
| Miscellaneous information from cemetery records | Parents: James and Janet HALLAHAN, 178 Hare Street, Kalgoorie, Western Australia. Native of Ross, New Zealand |
| Family/military connections | Brother of Wendell James, Walter Row MC, MM and Rolf Thomson. |