Mărdărescu was born in Iași, Romania on 4 August 1866. In 1888 he graduated from the Infantry and Cavalry Military School in Bucharest with the rank of second lieutenant, and was promoted to lieutenant in 1891. He pursued his military studies at the Higher War School from 1892 to 1894. He advanced in rank to captain in 1896, and on 10 May 1906 he was promoted to major and named commandant of the Infantry Shooting School. After being promoted to lieutenant colonel in 1910 and colonel in 1913, he was appointed Chief of Staff of 1st Army Corps. In 1915 he became Commandant of the School of Cavalry Officers at the Military Academy.
On 10 May 1916 he was promoted to brigadier general, and on 15 August he took command of the 18th Infantry Brigade. After Romania entered World War I on the side of the Allies on 27 August, Mărdărescu was appointed Chief of Staff of the 3rd Army and then the 2nd Army. Under the command of General Alexandru Averescu, he helped coordinate the Romanian Campaign of 1916, first in the Dobruja, and then during the defense of the Predeal Pass. Mărdărescu was later put in charge of 3rd Army Group (a command he held until 1917), and fought at the battles of Mărăști and Oituz in July–August 1917.[1] In February 1918 he advanced to divisional general.
In August 2019, on the occasion of the 100th anniversary of his victory in the Hungarian–Romanian War, a statue of Mărdărescu was unveiled on the campus of Babeș-Bolyai University in Cluj-Napoca.[2][3] Streets in Sibiu and Oradea bear his name.