TORONTO - Workers at Fiat Chrysler have voted to accept a new contract with the automaker in what their union describes as "tough" negotiations.

Unifor says the four-year agreement secures both investment and wage improvements.

The union says all of the bargaining units within Fiat Chrysler gave strong support for the deal in a vote held Sunday -- the agreement covers some 9,750 employees.

Unifor says the deal includes two wage increases of two per cent and signing bonuses that total $12,000 over the next four years.

The union says management promised to invest $331 million in its Canadian operations.

Union president Jerry Dias indicated before talks with both Chrysler and General Motors that investment was the most important issue for the workers.