The assessment criteria included use of recycled fibre, energy use and CO2 emissions, water consumption and water pollution.
WWF commended Mondi for its policy to eliminate all controversial timber supply sources - its current level of FSC-certified fibre content for fine paper production is 43.2%, the highest of the fine paper producers listed publicly.
David Hathorn, Mondi group chief executive, said: "We have a strong commitment to sustainable development and continuous improvement in reducing our environmental footprint.
"We hope that the index will attract many global paper companies as it provides an opportunity for participating companies to present progress they continue to make in reducing the impact of their operations on the environment."
Mondi has a green range of products that are FSC certified, chlorine-free paper or 100% recycled paper.
The company manufactures uncoated fine paper packaging paper and converted packaging products, as well as speciality products.
Mondi bags top honours in WWF eco ratings
Paper and packaging manufacturer Mondi has been rated the top company in WWF's voluntary rating tool for paper companies reporting on their global ecological footprint.
