| Regimental number | 1854 |
| Place of birth | Goondiwindi, Queensland |
| Religion | Roman Catholic |
| Occupation | Railway employee |
| Address | Chinchilla, Queensland |
| Marital status | Single |
| Age at embarkation | 32.2 |
| Height | 5' 10.5" |
| Weight | 175 lbs |
| Next of kin | Mother, Mrs Margaret Brennan, Goondiwindi, Queensland |
| Previous military service | Nil |
| Enlistment date | |
| Place of enlistment | Brisbane, Queensland |
| Rank on enlistment | Private |
| Unit name | 5th Light Horse Regiment, 13th Reinforcement |
| AWM Embarkation Roll number | 10/10/3 |
| Embarkation details | Unit embarked from Brisbane, Queensland, on board HMAT A55 Kyarra on |
| Rank from Nominal Roll | Driver |
| Unit from Nominal Roll | 2nd Field Artillery Brigade |
| Fate | Returned to Australia |
| Discharge date | |
| Family/military connections | Brothers: 4088 Pte Clarence Francis BRENNAN, 26th Bn, returned to Australia, 12 November 1919; Pte 57772 Corporal Malcolm Maurice BRENNAN, Signals Engineers Details, returned to Australia, 15 November 1919. |
| Other details |
War service: Egypt, Western Front Commenced return to Australia on board HT '', 27 August 1917; discharged (medically unfit: dislocation of 1st metatarsal), Brisbane, 27 November 1917. Medals: British War Medal, Victory Medal |
| Date of death | |
| Place of burial | Goondiwindi Cemetery, Queensland |
| Sources | NAA: B2455, BRENNAN William Vincent |