DEC may stand for:
- Derwent Entertainment Centre
- Dheeraj and East Coast LLC
- Distance Education Council
- Digital Equipment Corporation
- Diethylcarbamazine
- Diethyl carbonate, an ester
- Disasters Emergency Committee
- Department of Education and Communities (New South Wales), formerly known as the Department of Education and Training.
- Department of Environment and Conservation (Western Australia)
- Department of Environmental Conservation (New York)
- December
- Diplôme d'études collégiales, known in English as the Diploma of College Studies