| Regimental number | 58528 |
| Place of birth | Morpeth New South Wales |
| Religion | Roman Catholic |
| Occupation | Bricklayer |
| Address | Mayfield, New South Wales |
| Marital status | Single |
| Age at embarkation | 21 |
| Next of kin | Father, M J Brennan, Queen Street, Mayfield, West Maitland, New South Wales |
| Enlistment date | 12 March 1918 |
| Rank on enlistment | Private |
| Unit name | 1st to 15th (NSW) General Reinforcements |
| AWM Embarkation Roll number | 23/111/5 |
| Embarkation details | Unit embarked from Sydney, New South Wales, on board A40 Ceramic on 22 December 1914 |
| Embarkation details | Unit embarked from Sydney, New South Wales, on board HMAT A18 Wiltshire on 19 June 1918 |
| Embarkation details | Unit embarked from Sydney, New South Wales, on board SS Feldmarschall on 19 June 1918 |
| Unit from Nominal Roll | 53rd Battalion |
| Fate | Returned to Australia 20 September 1919 |
| Miscellaneous details (Nominal Roll) | Listed as John Sylvester Brennan on nominal roll |