Dalbert Isaac Hallenstein was born on 15 August 1893 at Heidelberg, Germany to Lucie Michaelis and Ruben Hallenstein. He was raised in Melbourne and attended Melbourne Church of England Grammar School. Before enlisting in the war, he worked for the family tanning business of Michaelis, Hallenstein & Co in Melbourne while also being a lieutenant in the 64th (City of Melbourne) Regiment.
Dalbert Isaac Hallenstein enlisted in the Australian Imperial Forces on 16 January 1915 as a second lieutenant and was assigned to the 2nd Reinforcements of the 5th Infantry Battalion. He embarked with the unit on 19 February 1915 from Melbourne on board the HMAT Runic. He served at Gallipoli until August 1915 when he was evacuated to Lemnos with Neurasthenia. While in Lemnos his condition worsened, and he was consequently sent to Alexandria to recover. He re-joined his battalion in February 1916, and by April he was taken on strength of the 57th Battalion. However, in May of 1916 he was transferred to the 5th Cyclist Battalion.
Hallenstein embarked to Marseilles with the 5th Cyclist Battalion in June 1916, and was attached to the 14th Machine Gun Company shortly after landing. By September of that year, his attachment to the 14th Machine Gun Company was changed to a transfer, and he was soon promoted to full lieutenant.
In April 1917, Hallenstein was wounded in action receiving a gunshot wound to the right wrist. He was sent to England to recover and re-joined his unit at the Western Front in August 1917. In February 1918, he attended the 4th Army Musketry School and returned to the 14th Machine Gun Company when he completed his course in March.

Dalbert Isaac Hallenstein was killed in action, on 2 September 1918, by a shell fragment when he took part in the attack on Peronne. His company of officer buried him in an adjacent trench and is now buried in Peronne Communal Cemetery Extension, Peronne, Picardie, France