The Norwegian primary aluminium producer already held a 50% stake in the business, but now owns the company outright.
All of the Vigeland refinery's high purity aluminium output is taken by Hydro and is said to fit in well with the company's value added product strategy.
High purity aluminium is a key component of semiconductors and LCD screens for televisions, computers, mobile phones and tablets.
Hilde Merete Aasheim, Hydro's executive vice president and head of primary metal, said the refinery was a good fit for Hydro's value-added product strategy.
The refinery, which has its own hydropower plant, is located on the Otra river at Vennesla and has an annual capacity of 8.5kt of high purity aluminium. The captive power plant produces 180GWh/yr.