Nathan River, owned by British Marine Group, was granted approval in February 2018 to ship existing stockpiles and process low-grade material.
The latest approval will see mining restart at a rate of up to 1 million tonnes per annum, for export through the Bing Bong port.
The mine has been on care and maintenance for the past five years and was acquired from the liquidators of Western Desert Resources.
"The decision by Nathan River Resources to invest in this project is a welcome boost for the resources sector, the Territory's economy and job opportunities for local people," NT minister for primary industry and resources Paul Kirby said.
"It is a sign of confidence in the NT as a place to invest and exemplifies the significant potential of the Territory's mining industry."
Nathan River CEO Stefan Murphy said over A$250 million had been spent on the project.
"Operations are scheduled to commence in quarter three this year, with more than 250 full-time positions expected across mining, haulage, marine and support functions," he said.
"We now look forward to working with our partners and suppliers in the Territory to refurbish the project's pit to port infrastructure over the coming months ahead of the resumption of iron ore exports."
