About 150 employees at Degelman Industries in Regina hit the picket line Monday.
The workers served strike notice last week and were then locked out by management over the weekend.
The company and the United Steelworkers union had negotiated a tentative contract late last year, but it was rejected by employees during a ratification vote.
The union says it is still willing to return to the bargaining table.
Degelman designs and produces machinery for Saskatchewan's construction and agricultural sectors.
