He is best known for his watercolor paintings of the architectural monuments of the medieval Armenian city of Ani, and for designing the currency and postage stamps of the first Republic of Armenia (1918–1920).

As a result of over 20 years devoted to art, Fetvadjian produced no less than 2,000 works, varying from pencil drawings to watercolors, that depicted historically significant churches, monasteries, chapels and palaces.

[2] Some of his most memorable works come from the watercolor paintings of the chapels, palaces, churches and monasteries at Ani which are "factual and literal depictions of the buildings.

[3] Following the creation of the First Republic of Armenia in 1918, the members of the country's Finance Ministry commissioned Fetvadjian to draw up the new currency (to replace the Russian ruble) and stamps for the nascent state.

Although approached by several prestigious American universities to publish his works, Fetvadjian ultimately donated all of his paintings and drawings to the National Gallery of the Armenian Soviet Socialist Republic.

[5] Fetvadjian's works were highly valued for preserving a visual memory of Armenian artwork that otherwise might have been lost forever during the turbulent years following the end of the Russian Empire.