Grigol Dadiani was enlisted in the Imperial Russian Page Corps in 1828 and took part in the war against the Ottoman Empire in 1829. He then served with his father until 1834, when he was commissioned as a poruchik of the Life Guards Grenadier Regiment in St. Petersburg. In 1844, Dadiani, promoted to colonel, was enlisted in the Life Guards Preobrazhensky Regiment, but he continued his service in the Caucasus. Made major-general in 1854, he commanded the Mingrelian and Gurian militias, composed of local irregulars, against the Ottoman army in 1855 and 1856, during the Crimean War. In 1857, he was officially made a member of the His Imperial Majesty's Retinue. Dadiani commanded the 1st Brigade of the Caucasian Grenadier Division from 1858 and 1859 and took part in the storm of Gunib and capture of Imam Shamil during the Caucasian War. Dadiani was promoted to lieutenant-general in 1860 and, further following the Russo-Turkish War (1877–1878), on the occasion of the semi-centennial of his military service, to the rank of adjutant general in 1880. His final promotion, just prior to his retirement, was the rank of general of the infantry in 1883.