Greenpeace said Tuesday the Indian conglomerate filed a defamation suit in the high court in Mumbai in response to a campaign against Essar's mining operations.
Essar issued a statement Monday saying action taken last week by Greenpeace caused "immense damage" to its reputation.
"Essar holds the defendants liable for damages and has accordingly, sought appropriate redress from both civil and criminal courts," it said.
Greenpeace activists last week climbed the side of the building housing Essar's headquarters in Mumbai, unfurling a banner saying the company is "killing forests" with its coal mine activities.
"We are being sued by Essar because their underhanded tactics have been exposed," Greenpeace said.
The advocacy group said 67 activists were arrested after the protest action.
The Wall Street Journal reports the mining activity in the central state of Madhya Pradesh still needs the government's approval to move forward.
Greenpeace activists last year were detained by Russian authorities following similar protests against oil drilling in arctic waters.