The UIA is composed of 92 Member Sections which are professional organisations most representative of architects in 98 countries in the world. Each Section functions independently at national level and acts as the liaison with Governments, other Member Sections and the Union itself through a secretariat responsible for UIA affairs.

Member Sections contribute towards the economic and financial vitality of the Union through the payment of membership fees which constitute the essential resources of the UIA.

They are geographically divided into 5 Regions: