Companies, organizations and government bodies

• MDA (museums), formerly the Museum Documentation Association
• MacDonald Dettwiler (formerly MacDonald, Dettwiler and Associates), a Canadian company
• Magen David Adom (Hebrew: מגן דוד אדום‎), the national aid organization of Israel
• Manicaland Development Association
• Mechatronics Design Association, a student association at the University of Toronto
• Media Development Authority, a statutory board in the Singapore government
• Missile Defense Agency, an agency of the Department of Defense
• Muscular Dystrophy Association

Computing and technology

• T-Mobile MDA, a series of T-Mobile branded phones
• Mail delivery agent, software that routes e-mail to its destination
• Microconnect Distributed Antennae, a kind of transmitter/receiver
• Mobile document access, the retrieval of documents using a mobile computer
• Model-driven architecture, a software design approach
• IBM Monochrome Display Adapter, a computer display standard
• Main Distribution Area, a part of Date Center Cabling topology
• Manufacturing Defect Analyzer

Biology

• Malondialdehyde, is the organic compound with the formula CH₂(CHO)₂.
• A genetics technique called Multiple Displacement Amplification
• MDa, a megadalton, or one million (10⁶) daltons, where a dalton is a synonym for an atomic mass unit or amu.
• 3,4-Methylenedioxyamphetamine, aka MDA

Other meanings

• Misuse of Drugs Act 1971 (c.38)
• MDA - refers to an anesthesiologist
• MDA (TV series)
• Master's in Development Administration, a master's level professional degree
• a country in Europe, MDA in ISO 3166-1 country code
• Multiple Discriminant Analysis
• Metal Deactivating Agent
• Minimum Descent Altitude in an Instrument approach (aviation)