| Regimental number | 3438 |
| Place of birth | Normanville South Australia |
| Religion | Presbyterian |
| Occupation | Clerk |
| Address | Kapunda, South Australia |
| Marital status | Single |
| Age at embarkation | 19 |
| Next of kin | Mother, Mrs Ailcie K Macmillan, Kalgoorlie Road, Largs Bay, South Australia |
| Previous military service | 80th Infantry |
| Enlistment date | 30 December 1916 |
| Rank on enlistment | Private |
| Unit name | 50th Battalion, 9th Reinforcement |
| AWM Embarkation Roll number | 23/67/3 |
| Embarkation details | Unit embarked from Adelaide, South Australia, on board HMAT A48 Seang Bee on 10 February 1917 |
| Rank from Nominal Roll | Private |
| Unit from Nominal Roll | 50th Battalion |
| Fate | Returned to Australia 19 September 1918 |
| Family/military connections | Brothers: 3439 Pte Douglas Gilchrist MACMILLAN MM, 50th Bn, returned to Australia, 12 May 1919; 466 Sergeant Hugh Cameron MACMILLAN, 11th Light Horse Regiment, returned to Australia, 15 February 1918. |
| Date of death | 3 October 1979 |
