Some of his early works included the mansion of V. P. Kochubei in Tsarskoye Selo, 1911–1912; the house of Prince S. A. Scherbatov in Novinski Boulevard in Moscow, 1911–1913; the village railway employees housing and the tuberculosis sanatorium at the Prozorovskaya station (now Kratovo) near Moscow, 1913–1923; central workshops of Kazan railway in Lyubertsy, 1916).

He was the chief engineer of the local Council of People's Commissars and was a member of the CEC of the Armenian SSR (1925–1936), sponsored the construction industry, designed the layouts of towns and villages including Leninakan (now Gyumri) (1925), Stepanakert (1926), Nor-Bayazet (now Gavar) and Ahta-ahpara (both in 1927), Echmiadzin (1927–1928), and others.

Tamanian's style was instrumental in transforming what was essentially a small provincial city into the modern Armenian capital, a major industrial and cultural center.

Neoclassicism dominated his designs but Tamanian also implemented a national flavor (red linings of tuff, traditional decorative carvings on stone etc.).

Among his most famous designs in Yerevan are the hydroelectric station (ERGES-1, 1926), the Opera and Ballet house named after A. Spendiarian (1926–1953), the Republic Square (1926–1941) and others.