The Northwestern Ontario Municipal Association is comprised of: 

• the Kenora District Municipal Association; 
• the Rainy River District Municipal Association, 
• the Thunder Bay District Municipal League; and,
• the City of Thunder Bay. 

Other than the City of Thunder Bay, membership is attained by being a member of the district organization. The Township of White River in the District of Algoma being a member of the Thunder Bay District Municipal League also has membership into NOMA.