| Dandelion Allergy Centre, Milton | Milton |
| Danton Medical Centre, Oakville, Family Practice and Walk-in | Oakville |
| Danton Pharmacy, Oakville, Pharmacy Services | Oakville |
| Dar Foundation | Oakville |
| Dar Foundation, Food Program | Oakville |
| Dawn of Angels Health, In Home Care Services | Burlington |
| Deaf Muslims of Canada, Interpretation / Translation | Burlington |
| Death Doula Ontario Network, Death Doula Ontario Network Resources | |
| DEBRA Canada | Oakville |
| Debtors Anonymous, Oakville - Mailing Address | Oakville |
| Deliverance Tabernacle Church of God | Burlington |
| Delmanor - Glen Abbey, Retirement Residence | Oakville |
| Derry Pharmacy, Pharmacy Services | Milton |
| Destiny Care Services, In Home Care Services | Mississauga |
| Developmental Services Ontario Central West Region, Access to Services and Supports for Individuals with a Developmental Disability | Milton |
| Diagnostic Imaging, Halton Hills | Halton Hills |
| Diagnostic Imaging, Oakville | Oakville |
| Dietitians of Canada - UnlockFood.ca, Dietitians of Canada | Toronto Downtown Central |
| directSmiles, Oakville, Mobile Dental Hygiene Services | Oakville |
| Distress and Crisis Ontario | Waterloo |
| Distress Centre Halton | Halton Region |
| Distress Centres of Greater Toronto, Survivor Support Program | Toronto |
| Doctors House Call Service - Concierge Medicine, In Home Doctor Services | Burlington |
| Dorval Medical Family Health Team | Oakville |
| DriveAgain, Driver Assessment Services | Burlington |
| DriveTest - Guelph, Guelph, DriveTest Centre | Guelph |
| DriveTest Centre, Burlington, Driver Examination Centre | Burlington |
| DriveTest Centre, Oakville, Driver Examination Centre | Oakville |
| Drury Lane Theatrical Productions | Burlington |
| DSUPREME, Mobile Service, In Home Care Services | Burlington |
| Dundas Neyagawa Medical Centre, Family Practice and Walk-in | Oakville |
| Dying With Dignity Canada | Toronto |
| Dynacare, Oakville - Old Bronte Rd, Laboratory and Health Services Centre | Oakville |
| Dynacare, Oakville - Bristol Circle, Laboratory and Health Services Centre | Oakville |
| Dynacare, Milton, Laboratory and Health Services Centre | Milton |
| Dynacare, Oakville - Oak Park Blvd, Laboratory and Health Services Centre | Oakville |
| Dystonia Medical Research Foundation Canada | Toronto Downtown Central |
