Dong Energy has acquired a 35% stake, while Macquarie owns 50% and original developer, local firm Swancor, retains a 15% share.
Swancor will continue as lead developer of the second 120MW phase, supported by Dong and Macquarie. It is scheduled to begin construction in 2019 following a final investment decision, Dong said.
In September 2015, Swancor named Siemens as its preferred supplier to the second phase, providing 30 4MW offshore turbines.
Two of those turbine models powered the first 8MW phase of the project, located 3km from northwest Taiwan, and which was completed in October 2016.
"We look forward to engaging in Formosa I and to accelerating Taiwan's first commercial-scale offshore wind project," said Dong CEO Samuel Leopold.
"With Swancor's local expertise, Macquarie's strong track record in renewables, and Dong Energy's 25 years of experience in offshore wind, we have formed a strong partnership to execute on this project."
In April 2016, Dong announced it was opening an office in Taiwan to "explore offshore wind opportunities in the Asia-Pacific region", with a particular focus on the country.
In August 2015, Taiwan's economic affairs ministry increased the country's offshore wind target from 3GW to 4GW by 2030.
Macquarie has been growing its investments in offshore wind projects. It is also the preferred bidder to acquire the UK's Green Investment Bank, despite some criticism.