 While in Saint Petersburg, Kajaznuni joined the Armenian Revolutionary Federation, eventually becoming one of its most important figures.After graduation, he worked at the construction department of the Baku provincial administration (1893–95), as an architect in Batumi (1895–97), and as regional architect at the Tiflis provincial administration (1897–99).Between 1899 and 1906, he worked as a senior architect in Baku, designing hospitals and apartment buildings, his most notable work being the Saint Thaddeus and Bartholomew Cathedral completed in 1911.