Incitec said its Dyno Nobel business had been awarded an explosives products and services supply contract with FMG from July 2018 to December 2023.
"Dyno Nobel is delighted to be partnering with Fortescue," Incitec managing director and CEO Jeanne Johns said.
"We have shared values of safety and a commitment to practical innovation."
The win comes after Incitec ceased to supply explosives and services to fellow Pilbara iron ore player Roy Hill in February.
The loss of that contract and Incitec's contractual commitments to its third-party ammonium nitrate supplier in Western Australia was expected to heavily impact profits out to FY22.
Incitec flagged a A$5 million impact to net profit after tax for this financial year, which remains unchanged.<...