Born into the Upper Saxon noble family of Eulenburg, August joined the army on 1 November 1856 as a grenadier in the 1st Foot Guard Regiment after his graduation from the Marienwerder Gymnasium.

He was promoted to second lieutenant two years later on 13 April 1858, and between 1860 and 1862 he participated in the trade mission in East Asia as an attaché under his kinsman Friedrich Albrecht zu Eulenburg.

[1] Eulenburg retired from active military service as a colonel in 1889, but was promoted to major-general in 1891 and lieutenant-general in 1895, before being made à la suite General of the Infantry on 18 October 1904.

[2] He continued to serve as Chief Representative (General-Bevollmächtigter) of the House of Hohenzollern after the November Revolution for the remainder of his life.

He died in 1921 in Berlin, and was buried in the Holy Trinity Cemetery in the Kreuzberg district alongside his family.