In its first move in to the German offshore wind sector, Parkwind bought the KNK Wind company, which was developing the site, from previous owners WV Energie for an undisclosed fee.
Parkwind and WV worked together on the successful auction bid, the Belgian firm said.
"We are delighted to take our first steps in the German offshore market," said Parkwind co-CEOs Francois Van Leeuw and Eric Antoons in a joint statement.
Arcadis Ost 1 was one of three Baltic Sea projects to secure support in the late-April auction.
The move follows Parkwind's acquisition of the 330MW Oriel wind project in Ireland in October 2017.
"After the acquisition of Oriel in 2017, this is our second step of many to come in growing Parkwind internationally," the company's chief executives said.
"We are constantly on the lookout for challenging projects and for the right partners to make them happen," they added.
Parkwind currently operates 546MW of offshore wind capacity in the Belgian North Sea: Nobelwind, Northwind and Belwind.
It also expects to complete financing for its 224MW Northwester 2 project this year, which is set to use MHI Vestas' V164-9.5MW turbines for the first time.