Marine Current Turbines (MCT) is an industry leader in tidal power and has developed a demonstration project at Strangford Lough in Northern Ireland.
Tidal power is forecast to grow rapidly to 2020 and has the potential to eventually generate more power every year than is consumed by Germany, according to Siemens.
The UK, with its strong tidal currents, is seen as a leading market. Energy from the waves and tides has the potential to meet as much as 20pc of current UK electricity demand, according to the government.
Ted Scheidegger, chief executive of the solar and hydro division of Siemens Energy, said: “The acquisition of Marine Current Turbines is an important step forward for the solar and hydro division.
"We will continue to drive the commercialisation of this promising technology which harvest energy from highly predictable tidal streams. Our target is to secure a leading position in this future business.”
MCT is planning further projects in Scotland and at Anglesey in Wales.
Andrew Tyler, chief executive, said: "Siemens’ acquisition is hugely welcomed by staff and management at MCT and signals great confidence in MCT’s achievements over many years."
Siemens already owned a 45pc stake in MCT and has taken that to 90pc. The financial details of the transaction have not been disclosed. The German company says it will take full control of the group over the next few weeks.