The union says the deals with Inteva Products, Lear Corp. Whitby, Auto Warehousing Canada and Robinson Solutions provide for improved severance packages for employees compared with the legislated minimum requirements.
It says they are the last of 11 it has negotiated at companies that will be hurt by the end of vehicle assembly at GM Oshawa.
The 11 agreements cover more than 1,200 workers represented by Unifor in the independent auto parts sector.
General Motors announced last November that the Oshawa assembly plant would close at the end of this year.
The automaker has agreed to convert the operation to a part-stamping and autonomous vehicle testing facility in a move that will save about 300 of the 2,600 union jobs at the plant.