Both the firms did not disclose the financial terms of the transaction.
Tokyo-headquartered GPI was established in 2004 by Toshio Hori, its current CEO.
The company spent several years co-managing a fund and developing renewable energy projects in Europe. It is currently focused on further expanding its development and investment activities in Japan.
Pattern Energy president and CEO Mike Garland said: "Pattern Development will combine its resources and support with GPI to continue its strong commitment to helping Japan meet its renewable energy goals and reduce reliance on imported fossil fuels.
"GPI has a number of projects in various stages of development and we look forward to providing more detail in the coming months."
The projects will be added to Pattern Energy’s right of first offer (ROFO) list, which represents near-term acquisition opportunities.
Renewable energy firm Pattern Development owns about 35% of Pattern Energy, which has the ROFO to acquire projects developed by Pattern Development.
Pattern Development’s project pipeline stood at 3,500MW prior to the GPI transaction.
Pattern Development has more than 3GW of wind, solar, and several transmission projects in development. The company’s global footprint currently spans across North America, South America, the Caribbean and Japan.
