Anton Lehár was born at Ödenburg (Sopron) on the 21st of February 1876. His father was the Regimentskapellmeister (bandmaster) of infantry regiment number 50, but whilst his elder brother Franz Lehár went on to become a celebrated composer, Anton entered, after finishing the Realschule, the Infanteriekadettenschule at Vienna to become a professional officer. He left the cadet school in 1893 as the best of his age-class becoming a Kadettoffiziersstellvertreter in infantry regiment number 50 where he was commissioned as a Leutnant in 1894. He received the rank of Oberleutnant whilst he was at the Kriegsschule (1897-1899) on the 1st of November 1898. In May 1900 Oberleutnant Lehár was attached to the general staff. In May 1902 he was promoted to Hauptmann 2nd class and transferred to infantry regiment number 83 where in May 1906 he was promoted to Hauptmann 1st class. He was then attached to the technical Militärkomitee performing duty as an instructor at the Armeeschießschule (army school of musketry) at Bruck an der Leitha, where he was honored with award of the military merit cross in April 1909, a certificate of appreciation from the war ministry in October of the same year and the bronze military merit medal (Signum Laudis) in April 1913. During his period as a musketry instructor Anton Lehár was also honored by foreign awards ; the officers' cross of the order of the Star of Rumania in August 1911 and the 4th class of the Ottoman Osmanie Order in April 1913. He remained at this post after he passed the general staff examination for senior officers and received the rank of Major in November 1913.
Following the outbreak of the war Anton Lehár assumed command of the 2nd battalion of the Honvéd-Landsturm infantry regiment number 13, which was subordinated to Generalmajor Georg Mihálcsics von Stolácz's Landsturm Infantry Brigade 100 of Armeegruppe Kummer which was recruited from the Pressburg area. On the 2nd of September 1914 the Russian 4th army counterattacked south of Lublin. Particularly hard hit was the position at Chodel which formed the boundary between General der Kavallerie Viktor Dankl's 1st army and Army Group Kummer. For his command of this battalion at Chodel and the holding of trig point 229 on the 2nd of September 1914 Major Lehár was to be decorated with the knights' cross of the Military Maria Theresia Order and to be ennobled with the predicate "Freiherr von" in August 1918.
Leading this battalion near Lublin on the 7th of September 1914 he was severely wounded and whilst he was in hospital he received the Orden der Eisernen Krone 3.Klasse mit Kriegsdekoration (3rd class of the order of the Iron Crown with war decoration) in October 1914. To assist his recovery he was transferred to the general staff's department of the Landesverteidigungskommando of the Tyrol (Tyrolean Defence Command). There he received his promotion to Oberstleutnant on the 1st of September 1915 and the Prussian Iron Cross 2nd class in October 1915. At his own request he was transferred back to the front and took over the command of the Etschtal-Rovereto sector on the Italian front. In summer 1916 he was transferred back to the technical Militärkomitee as Abteilungsvorstand für die Infanterie-und Kavalleriebewaffnung (Department Head for infantry and cavalry weapons). In this position he made a strong effort to get more machine guns to the troops especially at company level. Again following a personal request he was transferred back to the front and assumed command of the Landsturmbataillon number 150, mainly recruited from Styria in the autumn of 1917. Following action in the Bukovina he was transferred to the Piave front where he took over the command of the newly raised infantry regiment number 106 in January 1918. As commander of this regiment he earned the Golden Bravery Medal for Officers on the Piave and received his promotion to Oberst on the 1st of May 1918. At the conclusion of hostilities he was able to get his entire regiment, without any causalities or desertion, back to Steinamanger (Kössegg).
Influenced by his brother Franz Lehár he decided to remain in Hungary fighting for the monarchy. In winter 1918/19 he was commander of an infantry division fighting against the Bolsheviks and relieved Lemberg. In the spring of 1919 he found himself as commander of a battalion of Hungarian emigrants fighting against the Yugoslavian army near Radkersburg in south Styria. In August 1919 he took over the command of the (royal-Hungarian) division at Szombathely becoming the military commander of Western Hungary and receiving the promotion to Generalmajor by Reichsverweser (Regent) Admiral Horthy. When Kaiser Karl tried to regain his Hungarian crown he immediately joined his troops, but the mission failed and while the Kaiser was transported into exile Generalmajor Anton Freiherr von Lehár was hunted like a common criminal. He fled through Czechoslovakia to Germany where he was hidden by some friends of his brother. After the situation had calmed down his brother organized him a job as director of the society of authors, composers and music publishers in Berlin in 1926. As a dedicated monarchist he was always considered suspect by the national-socialist party and when they assumed power in 1933 he had to leave Berlin within hours. Back in Vienna he founded the "Chodel-Verlag" a small music publishing company but the strong arm of the nazis was long and so he decided to hand over the company to his brother in 1935 and moved to the countryside becoming a farmer near Theresienfeld in Lower Austria. He thought that the Nazi suppression would not be so strong outside the cities, but this was wrong. When nazi-Germany occupied Austria in March 1938 he was forced to sell his "Marienhof" and settle with his wife in Vienna where the Gestapo could keep a closer eye on him.
During this time of his de facto "house-arrest" he wrote his large "Erinnerungen" - published by Dr. Peter Broucek in 1973. After the death of his brother Franz Lehár in October 1948 he became the administrator of his (musical) estate and did his best to promote the popularity of his brother's music. Anton Freiherr von Lehár died in Vienna on the 12th of November 1962.