The company has acquired a 39% share in the 165MW Belwind 1 project, and a 30% holding in the 216MW Northwind project. It has purchased the stakes from Parkwind, a joint venture between Belgian retailers Colruyt Group and Korys NV and investment fund PMV.
Sumitomo also announced that it is "working together with Parkwind" on the 165MW Belwind 2 project, which is due to come online in 2018.
Belwind 1 and Northwind are both in the North Sea, with Belwind 1 located 46 kilometres from the coast, and Northwind 37 kilometres out to sea. Both feature Vestas 3MW turbines.
The Belwind project has been in operation since 2010. Construction of Northwind was completed in June 2014 and it also online.
Parkwind will continue to hold the remaining share of the projects. Financial terms of the deal were not revealed.