- Concordia Lutheran Ministries
- Cone Health Wesley Long Hospital
- Conemaugh Health System
- Conemaugh Memorial Medical Center
- Conemaugh Meyersdale Medical Center
- Conemaugh Miners Medical Center
- Conemaugh Nason Medical Center
- Conference and Logistics Consultants, Inc.
- Conference Archives Inc.
- Conference Direct
- Conference Direct
- Conference Direct
- Conferon, Inc.
- Confluence Technologies, Inc.
- Congregation Agudas Achim
- Congregation Kol Ami
- Congregational Health Ministry
- Congress of National Black Churches
- Congressional Black Caucus Foundation, Inc.
- Congressional Institute Incorporated
- Conley Group
- Connecticut Association of Not for Profit Providers for The Aging
- Connecticut Association of Not-For-Profit Providers for T
- Connecticut Association of School Business Officials
- Connecticut Children's Medical Center
- Connecticut Convention and Visitors Bureau
- Connecticut Primary Care Association
- Connecticut River Valley and Shoreline Visitors Council
- Connecticut State Legislature
- Connecticut VNA
- Connectivity Solutions man
- ConnectLife
- Connects Federal Credit Union
- Conoco
- Conoco Phillips
- Conor Medsystems
- Conotti Corporation
- Conquest Systems
- Conrad Public Library
- Conseco
- Consolation Reunion Committee, Inc.
- Consolidated Bank and Trust co.
- Consolidated Cigar Company
- Consolidated Contracting Services, Inc.
- Consolidated Engineers
- Consolidated Laboratory Services
- Constella Group
- Construction General Laborers Local 373
- Construction Management Consultant Group Corp
- Construction Specifications Institute