Mutual insurance companies in Ontario have memberships or regular business dealings with the following organizations:
| OMIA | Ontario Mutual Insurance Association (primary trade association) |
| FMRP | Farm Mutual Reinsurance Plan Inc. |
| CAMIC | Canadian Association of Mutual Insurance Companies |
| MAMIC | Maritime Association of Mutual Insurance Companies |
| NAMIC | National Association of Mutual Insurance Companies (U.S.) |
| FSCO | Financial Services Commission of Ontario |
| IBAO | Insurance Brokers Association of Ontario |
| IBC | Insurance Bureau of Canada |
| IIOC | Insurance Institute of Canada |