| D&K Footcare Services | Bradford West Gwillimbury |
| Daisy A Day Home Care, Barrie, Daisy Acres Assisted Living | Barrie |
| Danube Seniors Leisure Centre | Bradford West Gwillimbury |
| Deaf Access Simcoe Muskoka, Barrie Central Office, American Sign Language Classes | Barrie |
| Deaf Access Simcoe Muskoka, Barrie Central Office, American Sign Language Interpreting | Barrie |
| Deaf Access Simcoe Muskoka, Barrie Central Office, Community Support Services | Barrie |
| Deaf Access Simcoe Muskoka, Barrie Central Office | Barrie |
| Deaf Access Simcoe Muskoka, Barrie Central Office, Employment Services | Barrie |
| DeafBlind Ontario Services | Newmarket |
| Dietitians of Canada - UnlockFood.ca, Dietitians of Canada | Toronto Downtown Central |
| Distance Education. Ontario Colleges of Applied Arts and Technology | |
| Down Syndrome Association of Simcoe County, Mailing Address | Barrie |
| Dr. Dianne Maing Psychologist, Barrie | Barrie |
| Dragon Boat Barrie (Ontario), Mailing Address | Barrie |
| Drysdale's Tree Farm | Essa |
| Dufferin (County of). Municipal and Social Services, Orangeville - Edelbrock Centre, Employment Resource Centres | Orangeville |
| Dying With Dignity Canada | Toronto |