| A Cappella Showcase | Waterdown |
| A Child's Voice Foundation, Mississauga | Mississauga |
| A+ Medical Centre and Walk-In | Milton |
| Abbey Oaks Slo Pitch, Men's Slo Pitch League | Oakville |
| Abbeywood Pharmacy, Pharmacy Services | Oakville |
| Abilities to Work, Mississauga Location, Employability Health Support Services (EHSS) | Mississauga |
| Ability Clinic (The) | Dixie |
| Ability Concepts | Mississauga |
| Ability Online Support Network, Mono - Online Service | Mono |
| AbleLiving Services, Burlington - Westwood Hub, Community Outreach Services | Burlington |
| AbleLiving Services, Burlington - Bethany Residence, Supportive Housing | Burlington |
| AbleLiving Services, Burlington - Palmer Place, Supportive Housing | Burlington |
| Aboriginal Legal Services | Toronto |
| AboutFace | North York West |
| ABRAR Trauma and Mental Health, ABRAR Trauma and Mental Health Services | |
| Access Abilities, Medical Equipment Retailer | Oakville |
| Access Dental Care, Mobile Dental Hygiene Service | Mississauga |
| Access Midwives, Midwifery Services | Hamilton |
| Access Personal Support, In Home Care Services | Burlington |
| Accessible Media | North York East |
| AccessOAP | Toronto |
| Acclaim Health | Oakville |
| Acclaim Health, Burlington - Fairview St, Foot Care | Burlington |
| Acclaim Health, Burlington - Itabashi Way, Adult Day Program | Burlington |
| Acclaim Health, Mississauga Club, Adult Day Program | Mississauga |
| Acclaim Health, Community Support Services | Oakville |
| Acclaim Health, Friendly Visiting and Memory Visiting | Oakville |
| Acclaim Health, Home Care | Oakville |
| Acclaim Health, Home Support Exercise Program | Halton Region |
| Acclaim Health, Hospice Care and Bereavement Support | Oakville |
| Acclaim Health, Palliative Care Consultation | Oakville |
| Acclaim Health, Technology Accessibility Program | Oakville |
| Acclaim Health, Tele-Touch | Oakville |
| Acclaim Health, Adult Day Program - Soper Club | Oakville |
| Acclaim Health, Adult Day Program - Walmley Club | Oakville |
| Acclaim Health, Caregiver Education and Support | Oakville |
| Acclaim Health, JIM's Suites - Overnight Respite | Oakville |
| Acclaim Health, Patty's Place - Dementia Care Centre | Oakville |
| Achēv, Oakville, Newcomer Information Centre | Oakville |
| Achēv, Language Assessment Centres, Mississauga Location, Mississauga - 50 Burnhamthorpe Rd W | Mississauga |
| Achēv, Newcomer Information Centre, Mississauga Location | Mississauga |
| Achēv, Accelerating Career Advancement Program | Mississauga |
| Achēv, Oakville, Language Assessment Centre | Oakville |
| Acoustic Neuroma Association of Canada | Toronto |
| Across Boundaries: An Ethnoracial Mental Health Centre, Mental Health and Addiction Support Services | Toronto |
| Action Canada for Sexual Health and Rights | Ottawa |
| Active Aldershot Society | Burlington |
| Active Chefs | Oakville |
| ActiveMatch, Physical Activity Partnering Service for Cancer Survivors | Toronto Downtown Central |
| Acton Agricultural Society | Acton |
| Acton Aqua Ducks Swim Club | Acton |
| Acton Badminton Club, Recreational Badminton | Acton |
| Acton Citizens Band | Acton |
| Acton Curling Club | Acton |
| Acton Foodshare, Food Bank | Acton |
| Acton Horticultural Society | Acton |
| Acton Medical and Urgent Care | Acton |
| Acton Skating Club | Acton |
| Acton Soccer Club | Acton |
| Acton-Halton Walk-in Clinic | Acton |
| Acts of Kindness Network | Burlington |
| Ad Standards, Toronto | Toronto |
| ADAPT Halton, Oakville - Head Office, Alcohol, Drug and Gambling Assessment, Prevention and Treatment Services | Oakville |
| ADAPT Halton, Burlington Office | Burlington |
| ADAPT Halton, Community Justice Programs | Halton Region |
| ADAPT Halton, Community Withdrawal Management Services | Halton Region |
| ADAPT Halton, Concurrent Disorders Programs | Halton Region |
| ADAPT Halton, Georgetown Office | Georgetown |
| ADAPT Halton, Milton Office | Milton |
| ADAPT Halton, Problem Gambling & Behavioural Addictions Services | Halton Region |
| ADAPT Halton, Youth Programs | Halton Region |
| Adaptive Clothing, Halton Region | Ontario |
| Adoption Council of Canada | Ottawa |
| Adoption Council of Ontario | Toronto |
| ADR Institute of Ontario, Toronto | Toronto |
| Adult Learning Centre, Georgetown - Head Office, Essential Skills for Employment | Georgetown |
| Adult Learning Centre, Acton - Halton Hills Public Library | Acton |
| Adult Learning Centre, Burlington - Centre for Skills Development | Burlington |
| Adult Learning Centre, Literacy and Basic Skills | Halton Region |
| Adult Learning Centre, Milton - Centre for Skills Development | Milton |
| Adult Learning Centre, Oakville - Centre for Skills Development | Oakville |
| Adult Recreational League | Burlington |
| Adults in Motion, Day Program | Oakville |
| Advancement of Women Halton, Women's Advocacy Group | Halton Region |
| Advocacy Centre for Tenants Ontario | Toronto |
| Advocacy Centre for the Elderly | Toronto |
| Afghan Association of Ontario, Toronto | Toronto |
| African Community Services of Peel, Family Program | Brampton |
| African Community Services of Peel, Mental Health and Community Wellness | Brampton |
| African Community Services of Peel, Newcomer Settlement Program | Brampton |
| African Community Services of Peel, Violence Against Women Program | Brampton |
| AgeCare Brant, Long Term Care Home | Burlington |
| AgeCare Glen Oaks, Long Term Care Residence | Oakville |
| AgScape | Milton |
| Aiza's Teddybear Foundation | Oakville |
| Akwaba Cultural Exchange, Cultural Heritage Group | Milton |
| Al-Anon Family Groups, Halton Hills and Milton, Al-Anon and Alateen Meetings | Halton Hills |
| Al-Anon Family Groups, Hamilton / Burlington, Al-Anon / Alateen Meetings | Burlington |
| Al-Anon Family Groups, Oakville, Al-Anon / Alateen Meetings | Oakville |
| Al-Anon Family Groups, Al-Anon Family Groups, Ottawa - Canadian Headquarters | Ottawa |
| Alcohol and Gaming Commission of Ontario | Toronto |
| Alcoholics Anonymous, Oakville - Halton District Office, Halton Area Meetings | Halton Region |
| Alcoholics Anonymous, North Halton / Erin District, Erin and Area Meetings | Erin |
| Alcoholics Anonymous (GTA), Find an Alcoholics Anonymous Meeting - Greater Toronto Area Intergroup | Ontario |
| Alcoholics Anonymous Hamilton, Alcoholics Anonymous Meetings | Hamilton (City of) |
| Aldershot Community Recreation Association | Burlington |
| Aldershot Lions Club | Burlington |
| Aldershot Tennis Club | Burlington |
| Aldershot Village Business Improvement Area | Burlington |
| AlephCare, Mississauga, In Home Care Services | Mississauga |
| Al-Falah Islamic School, Private Elementary School | Oakville |
| Allendale Volunteers | Milton |
| Alliance for Healthier Communities | North York West |
| Alliance for South Asian AIDS Prevention, Toronto | Toronto |
| Alliance Francaise de Toronto, Oakville Campus, French Language Courses | Oakville |
| Alongside International | Burlington |
| Alpha Care Medical Center | Georgetown |
| Alpha Care Pharmacy, Georgetown, Pharmacy Services | Georgetown |
| Alpha's Discovery Kids Preschool and Daycare, Licensed Child Care Centre | Oakville |
| ALS Canada | Toronto Downtown Central |
| Alton Kids Child Care Center, Licensed Child Care Centre | Burlington |
| Altruvest Charitable Services | Milton |
| Always Best Care Senior Services, In-Home Care Services | Oakville |
| Alzheimer Society of Brant, Haldimand Norfolk, Hamilton Halton, Halton Office | Burlington |
| Alzheimer Society of Brant, Haldimand Norfolk, Hamilton Halton, Burlington Locations, Exercise Classes | Burlington |
| Alzheimer Society Peel | Port Credit |
| Alzheimer Society Peel, First Link | Mississauga |
| Alzheimer Society Peel, Behavioural Supports Ontario (BSO) | Port Credit |
| Alzheimer Society Peel, Counselling Services and Support Groups | Port Credit |
| Alzheimer Society Peel, Nora's House Respite Care | Port Credit |
| American Women's Club of Southern Ontario, Social Club | Oakville |
| Amica Bronte Harbour, Retirement Residence | Oakville |
| Amica Senior Lifestyles, Georgetown, Retirement Residence | Georgetown |
| Amnesty International Canada, Group 21 Burlington - Mailing Address | Burlington |
| Anglican Church of the Incarnation | Oakville |
| Angus Valley Montessori, Licensed Child Care Centre | Milton |
| Animal Control, Pest Control and Nuisance Animals, Burlington | Burlington |
| Anonymous Friend, Youth Peer to Peer Mental Health Support | Oakville |
| Aplastic Anemia and Myelodysplasia Association of Canada, Brighton | Brighton (Municipality of) |
| Appleby College | Oakville |
| Appleby College, Appleby Academy | Oakville |
| Appleby College, March Break Camps | Oakville |
| Appleby College, Newcomers Tutoring Program | Oakville |
| Appleby College, Summer Camp Programs | Oakville |
| Appleby Pharmacy, Pharmacy Services | Burlington |
| Appleby Tennis Club | Burlington |
| Appleby United Church | Burlington |
| Apples and Angels Montessori School and Day Care, Georgetown - 83 Main St, Licensed Child Care Centre | Georgetown |
| Apples and Angels Montessori School and Day Care, Georgetown - 79 Main St, Licensed Child Care Centre | Georgetown |
| Arcavia Home Care, Oakville, In Home Care Services | Oakville |
| ARCH Disability Law Centre | Toronto |
| Armenian Family Support Services | Toronto |
| Art Gallery of Burlington | Burlington |
| ArtHouse for Children and Youth | Oakville |
| Arthritis Society Canada, Burlington, Hamilton & Niagara Region Office, Community Support | Burlington |
| Arthritis Society Canada, Halton East and Peel Region, Mississauga | Mississauga |
| Artists' Legal Advice Services | Toronto |
| Arts & Culture Council of Burlington | Burlington |
| Arts Burlington | Burlington |
| Arts Milton | Milton |
| ARTSHINE Inc. / Arts4All | Kitchener |
| ArtWorks Oakville | Oakville |
| Arubah Kids Clinic | Mississauga |
| Ashwood Glen School, Licensed Child Care Centre | Burlington |
| Asian Community AIDS Services, Toronto | Toronto |
| Asperger's Society of Ontario | Toronto Downtown North |
| Aspira Retirement Living, Martindale Gardens, Retirement Residence | Milton |
| Assaulted Women's Helpline | Toronto |
| Assaulted Women's Helpline, Seniors Safety Line | Toronto |
| Assaulted Women's Helpline, Training, Resource and Outreach Department | Toronto |
| Assessment Review Board, Toronto | Toronto |
| Assisted Mobility Solutions | Georgetown |
| Associated Youth Services of Peel, Mississauga | Mississauga |
| Association for Bright Children of Ontario, Halton Chapter | Halton Region |
| Association of Oakville Harbours Stakeholders | Oakville |
| Association of Ontario Midwives | Toronto Downtown Central |
| Association of Translators and Interpreters of Ontario | Ottawa |
| Asthma Canada | Toronto Downtown North |
| Astra Fertility Group, Milton Clinic | Milton |
| Atwell Centre, Oakville, Pregnancy Support Services | Oakville |
| Aura Freedom International | Toronto |
| Ausum Charity for Autism | Streetsville |
| Autism Ontario, Halton Chapter - Mailing Address | Burlington |
| Autism Ontario | Toronto Downtown West |
| Automobile Protection Association | Toronto |
| Avanti Homecare, Milton, In Home Care Services | Milton |
| Avella Injury and Pain Management, Pain Management Services | Burlington |
| Average Joe Sports Club, Co-ed Recreational Sports Leagues | Oakville |
