Both the firms have "signed an agreement to acquire a controlling stake in Servion by investing Rs 403 crore (USD 66 million)", Everstone said in a statement.
The investment would be routed through Evertech Pte Ltd, an Everstone Group investing platform, the statement said.
Servoin specialises in providing customer interaction management (CIM) solutions to companies.
Everstone Managing Director Prateek Dhawan said:" Servion's cutting edge solutions and outstanding management team offer unique and strong investment opportunity."
Post-transaction, Dhawan would be joining Servion's board along with Solmark General Partner Puneet Pushkarna.