Cecil Beaumont Mills was born at Shellharbour, New South Wales on 15 October 1881. He was the son of John Beaumont and Esther (nee Gerrett) Mills. He attended Auburn Public School (where his father was Headmaster) and joined the English, Scottish and Australian (E.S.A) Bank in February 1898 as a probationary clerk and was made Manager of the Ascot Vale, Victoria Branch from 1913. Cecil married Effie Sara Burne, daughter of Dr Alfred and
Euphemia (nee Dangar) Burne on the 5 June 1913. Their only child, John Burne
Mills, was born on the 8 March 1915.

Having previously served the in the New South Wales militia, Cecil was appointed to the AIF as a second lieutenant on 25 October 1915. He was assigned to the 6th Reinforcement of the 23rd Battalion and Cecil, along with this unit, embarked at Melbourne on-board the HMAT Ulysses on the 27 October 1915. Upon arrival in Egypt, he attended the Officer's Training School in Zeitoun, and after he completed his training course he then moved to Tel-el-Kabir Camp.
Cecil embarked for France in March 1916, landed at Marseilles. He was promoted to Lieutenant on 1 May 1916 and saw action in Armentieres and the Somme.
Cecil was killed in action on 4 August 1916 during the battle of Pozieres. Private Harry Pettit in a letter to Cecil’s wife described Cecil’s death as the following“… It was while [he was] running across no man’s land to give instructions to some of his men when he was caught by machine gun fire and … it was instant”.

Cecil Beaumont Mills is commemorated on the Villers-Bretonneux Memorial in Villers-Bretonneux, France.