- Cardone Industries, Inc.
- Carl W. Herrmann
- Carl Walker Construction Group Inc.
- Carlisle Regional Medical Center
- Carlow College
- Carlson and Associates Real Estate Services, Inc.
- Carnegie Mellon University
- Carnegie Museums of Pittsburgh
- Carol Harris Staffing, LLC
- Catholic Charities of the Diocese of Pittsburgh, Inc.
- Cavanaugh Promotions
- CCRI
- Cdi Corp.
- Center for Bioethics - University of Pennsylvania
- Center for Organ Recovery and Education CORE)
- Centerville Clinics Inc.
- Centocor Inc.
- Central Pennsylvania Convention and Visitors Bureau
- Central Pennsylvania CVB
- Centre County United Way
- Chambersburg Hospital
- Chan Soon-Shiong Medical Center at Windber
- Chandler Hall Health Services - Doylestown
- Chandler Hill Health Services - Newtown
- Chatham University
- Chester County Convention and Visitors Bureau
- Chester County Hospital Penn Medicine
- Children's Hospital of Philadelphia
- CIGNA Corporation
- City of Erie
- City of Pittsburgh
- Civil and Environmental Consultants, Inc.
- Clarion Hospital
- Clarion Psychiatric Center
- Claude Worthington Benedum Foundation
- Clearfield Area United Way, Inc.
- Client Systems
- Clinical Trial Services
- Clinton County United Way
- Cole Memorial Hospital
- Columbia Lighting Corp.
- Comcast
- Commonwealth Health Regional Hospital of Scranton
- Commonwealth Health Wilkes-Barre General Hospital
- Communications Test Design, Inc
- Community Hospital, Crozer-Keystone Health System
- Community Integration Incorporated
- CommunityCare -Affiliated with Geisinger
- CompuData, Inc.
- Computer Science and Technology Inc.