The sale was made just a month after the HCMC-based energy firm began operating the wind power plant in Ninh Thuan Province, considered the nation’s largest to date.
After the deal, Hitachi SE will become a strategic partner in the project.
The group maintained that with the remaining 64.9 percent stake, it continued to play a decisive role in managing and developing the power plant.
The sale of shares to the Japanese investor will help raise more capital to implement other renewable energy projects, it said in a statement.
The wind power plant, which spreads over an area of 900 hectares in Thuan Bac District, has 45 turbines with a total capacity of 151.95 megawatts that is expected to generate some 432 million kWh per year. The plant has an investment of VND4 trillion ($173.4 million).
Last April, the private energy firm also sold a 49 percent stake in the VND5-trillion Trung Nam Thuan Bac Solar Power Plant in Ninh Thuan to A Chau Industrial Technology, an electricity equipment manufacturer.
Hitachi SE, along with its member companies, operates 30 wind power companies with a total installed capacity of 248MW in Japan.
Vietnam is said to have great potential for renewable energy production with its long coastline and 2,700 hours of sunshine a year on average.
Solar power currently accounts for just 0.01 percent of the country's total power output, but the government plans to increase the ratio to 3.3 percent by 2030 and 20 percent by 2050.
Vietnam aims to produce 10.7 percent of its electricity from renewable sources by 2030, mainly through solar and wind power projects.