GRI currently has 10 manufacturing facilities in Brazil, China, India, Spain, Turkey, and South Africa.
The company, which employs around 3,000 people, generated sales of €450m in 2014.
Mitsui and GRI will explore opportunities to set up new manufacturing plants in Asia, America and Europe.
The transaction, which is expected to be completed by the end of June 2015, is subject to approval from competition authorities.
Mitsui said it sees the equity participation as an opportunity to further improve the corporate value of GRI by using its strengths to build a better business base via the pursuit of synergies with its power generation activities.
GRI CEO Javier Imaz said: "The incorporation of Mitsui to GRI’s industrial project will allow us to accelerate and consolidate our internationalization process and to enter new energy-related sectors."
Mitsui said the increasing worldwide importance of energy generation using renewable sources such as wind and solar reflects various factors can reduce greenhouse gas emissions.
Wind power capacity is estimated to triple to more than 10% of total world generating capacity in the next 20 years.
Image: Gonvarri Eólica controls Spanish wind turbine tower and flange manufacturer GRI Renewable Industries Group. Photo: Courtesy of Mitsui & Co., Ltd.
