| A & B Clinics, Barrie, Virtual Addictions Clinic | Barrie |
| A & B Clinics, Barrie, Virtual Walk-in Medical Clinic | Barrie |
| A Trusted Senior Support Service, In-Home Support - Stephanie DiCeglie | Collingwood |
| A&A Piano/Violin Performance and Instruction, Barrie | Barrie |
| A. Farber & Partners, A.Farber & Partners Midland Bankruptcy and Consumer Proposal Office, Midland Bankruptcy and Consumer Proposal Office | Midland |
| Abilities In Motion | New Tecumseth |
| AboutFace | North York West |
| Academy of Learning Career College, Owen Sound | Owen Sound |
| Ace Transportation Group, Collingwood, Accessible Shuttle Service | Collingwood |
| Ace Transportation Group, Collingwood, Transportation Services | Collingwood |
| Achill Choral Society, Caledon | Caledon (Town of) |
| Ad Astral Place | Barrie |
| Ad Standards, Toronto | Toronto |
| Adams Funeral Home, Barrie, Grief and Bereavement | Barrie |
| AdaptABILITY Support Services, Barrie, Day Program | Barrie |
| AdaptABILITY Support Services, Barrie, Individual Adult Program | Barrie |
| AdaptABILITY Support Services, Barrie, Respite Services | Barrie |
| Addiction Services Central Ontario, South Simcoe Community RAAM - Alliston, Rapid Access Addiction Medicine Clinic, South Simcoe | New Tecumseth |
| Adjala-Tosorontio, Township of, Municipal Office | New Tecumseth |
| Adjala-Tosorontio, Township of, No physical address, Rest Stations for Extreme Weather Relief | Adjala-Tosorontio |
| Adjala-Tosorontio. Fire Service | New Tecumseth |
| Adoption Council of Ontario | Toronto |
| Adult Co-ed Recreational Soccer | Barrie |
| Advanced Nursing Foot Care, Mobile Service | Barrie |
| Advanced Nursing Footcare, Mobile Service | Barrie |
| Advocacy Centre for Tenants Ontario | Toronto |
| Advocacy Centre for the Elderly | Toronto |
| Advocis, Simcoe-Muskoka Chapter | |
| Afro-Caribbean Multi-Cultural Association, Barrie | Barrie |
| Age-Friendly Orillia Advisory Committee | Orillia |
| Agilec, Barrie, Integrated Employment Services | Barrie |
| Agilec, Innisfil, Integrated Employment Services | Innisfil |
| Agilec, Orillia, Integrated Employment Services | Orillia |
| Aging In Place - A Wonderful Life at Home | Wasaga Beach |
| AGTA Home Health Care Simcoe County | Barrie |
| Ahmadiyya Muslim Jama'at Barrie | Oro-Medonte |
| Ahmadiyya Muslim Jama'at Barrie, Ahmadiyya Muslim Youth Association Barrie | Oro-Medonte |
| Al-Anon, Angus / Borden, District 1 - Love and Hope Group | Adjala-Tosorontio |
| Al-Anon, Bradford, District 18 - Journey to Freedom Group | Bradford West Gwillimbury |
| Al-Anon, Orillia, Orillia - District 1 Muskoka | Orillia |
| Al-Anon / Alateen, Barrie - No Physical Address | Barrie |
| Al-Anon and Alateen Family Groups, Georgian Bay - No Physical Address, District 2 Georgian Bay | Owen Sound |
| Al-Anon and Alateen Family Groups, North Simcoe, Muskoka and Parry Sound - No physical address, District 1 - North Simcoe, Muskoka and Parry Sound | Bracebridge |
| Al-Anon. North Simcoe, Midland, Serenity Al-Anon Family Group | Midland |
| Alcohol and Gaming Commission of Ontario | Toronto |
| Alcohol and Gaming Commission of Ontario, Orillia, Regional Office | Orillia |
| Alcoholics Anonymous, Barrie, Barrie and Area Intergroup | Barrie |
| Alcoholics Anonymous, Western Georgian Bay District 9 | Owen Sound |
| Alcoholics Anonymous | Midland |
| Alcoholics Anonymous, Eastern Georgian Bay District 7 Area 86 | |
| Alcoholics Anonymous South Simcoe, Alliston, Alcoholics Anonymous | New Tecumseth |
| Alcoholics Anonymous South Simcoe, Borden CFB, Alcoholics Anonymous | Adjala-Tosorontio |
| Alcoholics Anonymous South Simcoe, Bradford, Alcoholics Anonymous | Bradford West Gwillimbury |
| Alcoholics Anonymous South Simcoe, Innisfil - Alcona, Alcoholics Anonymous | Innisfil |
| Alcoholics Anonymous South Simcoe, Innisfil - Stroud, Alcoholics Anonymous | Innisfil |
| Alcoholics Anonymous South Simcoe, Tottenham, Alcoholics Anonymous | New Tecumseth |
| Alectra | Vaughan |
| Alert Ready - Emergency Alert System | Ontario |
| All Saints' Anglican Church. Collingwood | Collingwood |
| All Saints' Anglican Church. Collingwood, Community Monthly Buffet Dinner | Collingwood |
| Alliston & District Humane Society | Adjala-Tosorontio |
| Alliston Business Improvement Association | New Tecumseth |
| Alliston Diagnostic Centre, Alliston, Medical Diagnostic Imaging and Consultation | New Tecumseth |
| Alliston Family Health Team | New Tecumseth |
| Alliston Food Bank, Alliston | New Tecumseth |
| Alliston Lions Club, Alliston Lions Christmas Food and Toy Hampers | New Tecumseth |
| Alliston Lions Club | New Tecumseth |
| Alliston Lions Club, Loan Cupboard | New Tecumseth |
| Alliston's Attic Thrift Store, Alliston - 39 Victoria St W | New Tecumseth |
| ALS Canada, Mailing Address, ALS Canada Community Services | Barrie |
| Alzheimer Society of Simcoe County, Barrie | Barrie |
| Alzheimer Society of Simcoe County, Barrie, Education Programs | Barrie |
| Alzheimer Society of Simcoe County, Barrie, Social/Recreational/Exercise Programs | Barrie |
| Alzheimer Society of Simcoe County, Barrie, Supportive Counselling | Barrie |
| Alzheimer Society of Simcoe County, Care Partner Support Groups, Barrie | Barrie |
| Am Shalom Synagogue, Barrie | Barrie |
| Amber Sperling Social Work and Psychotherapy, Barrie, Amber Sperling Social Work and Psychotherapy Services | Barrie |
| Amica Little Lake, Barrie | Barrie |
| Anglican Parish of Penetanguishene | Penetanguishene |
| Anglican Parish of Penetanguishene, All Saints Anglican Church - Penetanguishene, Breakfast Club | Penetanguishene |
| Angus and District Lions Club, No Physical Address | Essa |
| Angus Cooperative Homes | Essa |
| Angus Food Bank | Angus |
| Anishinabek Police Service, Christian Island Detachment | Beausoleil First Nation |
| Arcadia Home Care, Mailing Address | Toronto |
| ARCH Disability Law Centre | Toronto |
| Army, Navy and Air Force Veterans in Canada, Barrie, Barrie Unit 365 - Ladies Auxiliary | Barrie |
| Army, Navy and Air Force Veterans in Canada, Barrie, Barrie Unit 365 | Barrie |
| Army, Navy and Air Force Veterans in Canada, Orillia, Unit 400 Orillia | Orillia |
| Arrow Medical, Barrie - Dunlop St W, Methadone Clinic | Barrie |
| Arrow Medical, Barrie - Essa Rd, Methadone Clinic | Barrie |
| Arthritis Society Canada | Toronto Downtown Central |
| ArtTherapyWorks, Online/Telephone Service, Artworks, Counselling and Psychotherapy | Barrie |
| Ask4Care Support Services, Barrie | Barrie |
| Askennonia Senior Centre | Midland |
| Aspira Barrieview Retirement Community | Barrie |
| Aspira Waterford Barrie Retirement Living | Barrie |
| Aspire Community & Developmental Services | Barrie |
| Assaulted Women's Helpline | Toronto |
| Assisted Adult Living | Wasaga Beach |
| Association of Administrative Professionals, Barrie / Simcoe County Branch | Barrie |
| Association of Ontario Doulas, No Physical Address | Toronto |
| Association of Parent Support Groups in Ontario | Aurora |
| Assured Response CPR & First Aid Training | Barrie |
| AURA, Toronto | Toronto |
| Aura Freedom International | Toronto |
| Autism Ontario [Central East] | Toronto |
| Automobile Protection Association | Toronto |
| Avail Medical, Cannabis Clinic, Orillia | Orillia |