On the morning of 9 May, Tegetthoff learned that a Danish squadron consisting of the steam frigates "Niels Juel" and and the corvette were patrolling off the island of Heligoland. Tegetthoff took the five ships under his command out to attack the Danish vessels, resulting in the Battle of Heligoland. "Preussischer Adler" and the other Prussian ships remained on the disengaged side of the Austrian frigates, taking shots at the Danish vessels when possible, though they had little success. After "Schwarzenberg" caught fire, Tegetthoff broke off the action and escaped to the neutral waters around Heligoland, where the ships remained until early the next day. During the period off Heligoland, the Prussian vessels sent their doctors to the Austrian frigates to help tend to their wounded. "Preussischer Adler" had not been hit or suffered any casualties. The next morning, the ships returned to Cuxhaven, with "Preussischer Adler" carrying many of the wounded to a hospital at Altona. Though the Danish squadron had won a tactical victory at Heligoland, the arrival of Austrian warships in the North Sea forced the Danes to withdraw their blockade.