- OndeCare
- One Call Care Management
- One Equity Partners
- One Home Care Solutions LLC
- One Medical
- OneCare
- onehome
- OnShift
- Open Systems Healthcare
- OpenPlacement
- OPO Health
- Oppenheimer & Co.
- Opportunity Lives
- Optima Health
- Optima Health Plan
- Optima Healthcare
- Optima Healthcare Solutions
- Optimal Care Inc.
- Optimal Home Care
- Option Care