Statoil now owns 35% and will continue as operator of the project. Statkraft holds the remaining 30%.
The United Arab Emirates-based renewable energy company said the UK was "a major market for investment in offshore wind".
It is the second time Masdar has invested in the UK offshore sector. It holds a 20% share in the 630MW London Array – the world's largest operational offshore wind project.
Dudgeon is located 32 kilometres off the UK's east coast. Its Norwegian developers made a final investment decision in July and construction is due to begin in 2016. It will use 67 Siemens 6MW turbines.
The development was one of five offshore projects to qualify to claim subsidies under the UK government's new Contracts for Difference scheme.