During the Danish-Hanseatic war Barnim VIII took part in the privateering by Denmark against the Hanseatic League.

They captured a convoy or Hanseatic trading ships en route into the Baltic Sea.

In 1441, Barnim conquered the Zingst peninsula from the Cistercian St. Nicholas Abbey at Hiddensee.

[3] With the consent of his cousins, he later pledged the dominions of Barth, Zingst and Damgarten to his niece Catherine of Werle for 20000guilders.

They had a daughter Agnes (1434–1512); she married firstly, in 1449, Margrave Frederick III "the Fat" of Brandenburg (c. 1424-1463), and secondly, in 1478 Prince George II of Anhalt-Dessau.