The licence was suspended after the unit, NFC Africa, failed to comply with some conditions.
The agency, which must approve all large infrastructure projects, gave NFC Africa the go-ahead in 2012 for the South East Ore Body project about 400 km northwest of Lusaka, which would add 60,000 tonnes to Zambia's copper output.
But the company did not fulfill a requirement to prepare a comprehensive resettlement plan for people affected by the project, prompting the environmental agency to suspend the licence in December 2013.
"The order has been lifted. NFC Africa has been given three months to address the areas of concern," Ireen Chipili, the spokeswoman of the environmental agency, told Reuters.
NFC Africa plans to build a copper processing plant and sink four shafts for production, services and ventilation, according to a document submitted to the environmental agency.
The South East Ore Body has copper ore reserves estimated at more than 76 million tonnes, with an average grade of 2.18 per cent, the document said.