| 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. Farber & Partners, A.Farber & Partners Midland Bankruptcy and Consumer Proposal Office, Midland Bankruptcy and Consumer Proposal Office | Midland |
| Abbott Foot and Ankle Clinic | Collingwood |
| Abilities, Rehabilitation Services, Abilities Rehabilitation Services | Midland |
| Abilities In Motion | New Tecumseth |
| Ability Online | Etobicoke |
| AboutFace | North York West |
| Academy of Learning Career College, Owen Sound | Owen Sound |
| Ace Cabs, Accessible Shuttle Service | Collingwood |
| Ace Cabs | Collingwood |
| Ace Transportation Group, Collingwood, Transportation Services | Collingwood |
| Achill Choral Society, Caledon | Caledon (Town of) |
| Action CIND | Ramara |
| Ad Astral Place | Barrie |
| Ad Standards | Toronto |
| Adams Funeral Home, Barrie, Grief and Bereavement | Barrie |
| AdaptABILITY Support Services, Day Program | Barrie |
| AdaptABILITY Support Services, Individual Adult Program | Barrie |
| AdaptABILITY Support Services, Respite Services | Barrie |
| Addiction Services Central Ontario, Stevenson Memorial Hospital - 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 Foot & Orthotic Clinic | Midland |
| 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 | Barrie |
| Afro-Caribbean Multi-Cultural Association, Barrie | Barrie |
| After the Curb, No Physical Address | 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 |
| 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 | |
| Al-Anon and Alateen Family Groups, Wasaga Beach - No Physical Address, District 1 - Wasaga Beach | Wasaga Beach |
| Al-Anon. North Simcoe, Midland, Serenity Al-Anon Family Group | Midland |
| Alcohol and Gaming Commission of Ontario, Head Office | 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 Alliance Church | New Tecumseth |
| Alliston and District Mens Masters Slo Pitch League | New Tecumseth |
| Alliston Chiropractic Wellness Centre | New Tecumseth |
| Alliston Community Christian School, Alliston - 39 Victoria St W, Alliston's Attic Thrift Store | New Tecumseth |
| Alliston Community Christian School | New Tecumseth |
| Alliston Dental Hygiene Clinic | 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 Pentecostal Church | New Tecumseth |
| Alliston Physiotherapy and Sports Rehabilitation Clinic | New Tecumseth |
| Alpine Ontario, Collingwood, Southern Ontario Division | Collingwood |
| 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 |
| Amica Little Lake, Barrie | Barrie |
| Anchor Point Church, Alliston - 19 Victoria St E | New Tecumseth |
| Anglican Parish of Penetanguishene | Penetanguishene |
| Anglican Parish of Penetanguishene, All Saints Anglican Church - Penetanguishene, Breakfast Club | Penetanguishene |
| Angus and District Lions Club | Essa |
| Angus Cooperative Homes | Essa |
| Angus Food Bank | Angus |
| Angus Horticultural Society | Essa |
| Anishinabek Police Service, Christian Island Detachment | Beausoleil First Nation |
| Anten Mills Community Association | Barrie |
| Antique and Classic Car Club of Canada. Nottawasaga Region | Collingwood |
| Approachable Interior Design, Advantage Property Improvements, Property and Home Maintenance for Seniors and Persons with Disabilties | Midland |
| 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 |
| Art Therapy Works, Online/Telephone Service | Barrie |
| Arthritis Society Canada | Toronto Downtown Central |
| Arts Orillia, Creative Nomad Studios | Orillia |
| Ask4Care Support Services, Barrie | Barrie |
| Askennonia Senior Centre | Midland |
| Asperger's Society of Ontario | Toronto Downtown North |
| Aspira Barrieview Retirement Community | Barrie |
| Aspira Waterford Barrie Retirement Living | Barrie |
| Aspire Community & Developmental Services | |
| Assaulted Women's Helpline | Toronto |
| Assisted Adult Living | Wasaga Beach |
| Association of Administrative Professionals, Barrie / Simcoe County Branch | Barrie |
| Association of Day Care Operators of Ontario (The) | St Catharines |
| Association of Hearing Instrument Practitioners of Ontario | Lindsay |
| Association of Ontario Doulas, No Physical Address | Toronto |
| Association of Parent Support Groups in Ontario | Aurora |
| Assured Response CPR & First Aid Training | Port McNicoll |
| Atlantic Challenge Canada, Bay Port Yachting Centre - Midland | Midland |
| AURA | Toronto |
| Aura Freedom International | Toronto |
| Autism Ontario [Central East] | Toronto |
| Automobile Protection Association | Toronto |
| Avail Medical, Cannabis Clinic, Orillia | Orillia |
| AWARE Simcoe | Simcoe County |
| Aware Within, Collingwood, Michele Wolf, Psychotherapy, Counselling, Holistic Healing | Collingwood |