| | Organization Name(s) | Located In |
 | M S Chi Cheemaun, The Owen Sound Transportation Company Limited, Tobermory - Manitoulin Island Ferry, Ferry Services | Tobermory |
| | Mad Science of Niagara | St Catharines |
| | MADD, Niagara Region Chapter | St Catharines |
 | Magnolia Manor | Port Robinson |
 | Maid of the Mist Steamboat Company Ltd, Maid of the Mist Tour | Niagara Falls |
| | Main and Ferry Bia (Business Improvement Area) | Niagara Falls |
 | Main Street Baptist Church | Niagara Falls |
 | Mainstream, Options Niagara, A Foundation Initiative | St Catharines |
 | Mainstream, Resource Centre | St Catharines |
 | Mainstream, St Catharines Mainstream Non-Profit Housing Project | St Catharines |
 | Maison d'Amis Inc (House of Friends) | Fort Erie |
| | Mandolin Orchestra of Niagara | Welland |
 | Maple Leaf Marksman Club | Lincoln |
 | Maple Leaf Montessori School NOTL | Niagara-on-the-Lake |
 | Maplecrest Village | Grimsby |
| | Marathon Bridge Group | Niagara Falls |
 | March of Dimes Canada, Home And Vehicle Modification Program | London |
 | March of Dimes Canada, Niagara Outreach Attendant Services, Brock University/Niagara College On Campus Attendant Care | Thorold |
 | March of Dimes Canada, Personal Effectiveness Training | St Catharines |
 | March of Dimes Canada, St Catharines Office, Employment Services | St Catharines |
 | March of Dimes Canada, Stroke Recovery Canada, Survivors of Stroke West Niagara | Beamsville |
 | March of Dimes Canada, Supportive Housing Program, Faith Lutheran Villa | St Catharines |
 | March of Dimes Canada, Supportive Housing Program, Ridley Service Centre | St Catharines |
 | March of Dimes Canada, Supportive Housing Program, Scott Street Service Centre | St Catharines |
 | March of Dimes Canada, Supportive Housing Program, Stamford Kiwanis Manor Service Centre | Niagara Falls |
 | March of Dimes Canada, Warmline for Stroke Recovery Canada & Post-Polio Canada | Toronto |
 | March of Dimes Canada - South, Wellness Supportive Living Program, Buckley Towers | Niagara Falls |
 | March of Dimes Canada - South, Wellness Supportive Living Program, Jubilee Apartments and HUB | Welland |
 | March of Dimes Canada - South, Wellness Supportive Living Program, Kenworth Acres and HUB | St Catharines |
 | March of Dimes Canada - South, Wellness Supportive Living Program, Senior Citizens Apartments | St Catharines |
 | March of Dimes Canada - South Region, Thorold Office | Thorold |
| | Margaret Hertzberger - Adoption Search Consultant | Thorold |
 | Marineland | Niagara Falls |
| | Market Square | St Catharines |
 | Martindale Place | St Catharines |
| | Masons of Niagara A District | Niagara Region |
| | Masons of Niagara B District | Niagara Region |
| | Mastectomy Products | Niagara Region |
| | Master Gardener Hotline of Niagara Region | St Catharines |
 | Matthew 25 Niagara | Welland |
 | Matthew House | Fort Erie |
| | Maxxam, Forensic & DNA Testing, Human DNA Department | Guelph |
| | May Court Club of St Catharines | St Catharines |
 | Mayer Institute (The) | Hamilton Central |
 | Mayholme Foundation | St Catharines |
 | McGillivray & Associates, OT4KIDS | St Catharines |
 | McNally House, Niagara West Community Hospice | Grimsby |
| | Meals for Life | St Catharines |
 | Meals on Wheels Niagara Falls Ontario Inc | Niagara Falls |
 | Meals on Wheels Port Colborne Inc | Port Colborne |
 | Meals on Wheels Thorold-St Catharines | Thorold |
 | Melissa Bollinger, MSW, RSW, Psychotherapy and Counselling | St Catharines |
| | Mercredi Musique String Ensemble | St Catharines |
 | Merritton Bowling Leagues | St Catharines |
| | Merritton Community Group | St Catharines |
 | Merritton Figure Skating Club | St Catharines |
 | Metis Nation of Ontario, Aboriginal Healthy Babies/Healthy Children | Welland |
 | Metis Nation of Ontario, Community Support Service, Welland Council | Welland |
 | Millennium Trail Manor | Niagara Falls |
 | Minor Emergency Walk in Clinic | St Catharines |
 | Monica's of Welland | Welland |
 | Montebello Place Inc, Homes for Special Care, Group Home | St Catharines |
| | Mood Disorder Support Group of the Niagara Region | St Catharines |
 | Morgans Point United Church | Wainfleet |
 | Morrison St Walk-in Clinic | Niagara Falls |
 | Morse & Son Funeral Home & Morgan Funeral Home, Morse and Son Family Care Centre, Bereavement Support Program | Niagara Falls |
 | Mother Risk Program | Toronto (City of) |
 | Motion Specialties | St Catharines |
| | Motor Vehicle Accidents | Canada |
 | Mount Carmel Spiritual Centre | Niagara Falls |
 | Mountain Park Church | Niagara Falls |
 | Mouradian Group Inc, The | St Catharines |
 | Mr Pumpkin | Niagara Falls |
 | MTO St Catharines Toastmasters | St Catharines |
 | Multicultural History Society of Ontario | Toronto |
| | Multicultural Network of Niagara Falls | Niagara Falls |
 | Multiple Sclerosis Society of Canada, Ontario Division | Toronto (City of) |
 | Multiple Sclerosis Society of Canada, Ontario Division, Niagara Peninsula Chapter of Hope | St Catharines |
 | Municipal Property Assessment Corporation, MPAC, Central and Western Regional Operations Branch | St Catharines |
 | Muscular Dystrophy Canada | Toronto (City of) |
| | Music for Young Children, Grimsby | Grimsby |
| | Music for Young Children, Niagara Falls | Niagara Falls |
 | Music for Young Children, St Catharines | St Catharines |
 | Music for Young Children, Welland | Welland |
 | Music Niagara | Niagara-on-the-Lake |
 | Mutual Support Systems of the Niagara Region | Fenwick |
 | Myalgic Encephalomyelitis Association of Ontario | North York East |