- 1833 Coffee and Tea Co.
- 84 Lumber
- Abington - Jefferson Health
- Abington - Lansdale Hospital Jefferson Health
- Acculogix
- Achieva
- Acme Markets
- ACMH Hospital
- Acts Retirement Life Communities Inc.
- Acurian
- Adagio Health Council
- Adam's Mark Philadelphia
- Adams County Association for the Blind
- Agriculture Research Service, Wyndmoor
- AHN Canonsburg Hospital
- AHN Forbes Hospital
- AHN Grove City
- AHN Jefferson Hospital
- AHN Neighborhood Hospitals
- AHN Saint Vincent Hospital
- AHN West Penn Hospital
- AHN Wexford
- AIM, Inc.
- Akoya
- Albert Gallatin Home Care and Hospice
- Albright Care Services
- Alcoa Technical Center
- Allegheny County Bar Association
- Allegheny General Hospital
- Allegheny General Hospital-Suburban Campus
- Allegheny Intermediate Unit
- Allegheny Valley Hospital
- Altoona Curve
- Aluminum Consultants Group, Inc.
- Amalgamated Transit Workers Local 85
- Ambulatory Anesthesia Associates
- American Bridge Company
- American College of Physicians
- American Express
- American Program Underwriters
- AMETEK, Inc.
- Ampco-Pittsburgh Corporation
- Anchor Glass Containers Corporation
- Apostolou Associates
- Appligent
- APT Information Technology Consultants
- Aqua America
- Aria - Jefferson Health Bucks County
- Aria - Jefferson Health Torresdale
- Artman