EXHIBIT 21

Matrix Service Company

Subsidiaries

Matrix Service Inc., an Oklahoma corporation

Matrix Service Canada ULC, an Alberta, Canada unlimited liability corporation

Matrix North American Construction, Inc., an Oklahoma corporation

Matrix North American Construction, Ltd., a Canadian corporation

Matrix North American Construction, LLC, a Delaware limited liability company

Matrix SME Canada, Inc., a Delaware corporation

Matrix SME Canada ULC, a Nova Scotia, Canada unlimited liability corporation

Matrix PDM Engineering, Inc., a Delaware corporation

Matrix PDM, LLC, an Oklahoma limited liability company

Matrix Applied Technologies, Inc., a Delaware corporation

Matrix International Holding Company, Ltd., a British corporation

Matrix Applied Technologies, Ltd., a South Korean corporation

Matrix Applied Technologies, Pty. Ltd., an Australian corporation

River Consulting, LLC, a Louisiana limited liability company

Matrix Products and Services S. de R.L. de C.V., a Mexican limited liability variable stock corporation

Matrix Service VI, LLC, a U.S. Virgin Island limited liability company

Mobile Aquatic Solutions, Inc., an Oklahoma corporation

MSI Federal Contracting, LLC, a Delaware limited liability company

Devco USA, LLC, an Oklahoma limited liability company

Houston Dynamics, LLC, a Qatar limited liability company

Matrix Service International, LLC, a Delaware limited liability company

Matrix Applied Technologies FZ-LLC, a UAE free zone company

Matrix Applied Technologies Pte Ltd, a Singapore limited company

Matrix PDM Engineering Ltd., a Nova Scotia limited company