Dieter had shaggy blond hair and light bluish-gray eyes. He wore the typical uniform of the Scout Regiment.
Dieter appeared to be very unconditioned as a soldier. He showed great distress over the death of his friend Ivan, and disobeyed his superiors when they refused his request to retrieve Ivan's body; resulting in the death of his friend Jurgen. When confronted by Captain Levi, Dieter bursted into tears, cracking under the mental stress he had endured. Though he shows passion for his friends, this passion manifested itself in the form of recklessness, resulting in comrades' deaths.
During the 57th expedition, Dieter and his friend Jurgen argue with Erwin and Levi after they refuse their request to retrieve the body of their dead friend, Ivan. After Erwin decides to abandon all the bodies, Dieter and Jurgen act against orders and retrieve Ivan's body, inadvertently attracting several Titans to the Scout Regiment's position in the process.
Jurgen is grabbed off his horse and despite Dieter switching to his omni-directional mobility gear in an attempt to save him, Jurgen is eaten, and Dieter is grabbed by a Titan. Before the Titan can devour Dieter, Mikasa Ackermann kills it, saving him.
After this incident, Levi confronts Dieter and hands him Ivan's Scout Regiment badge, causing Dieter to break down into tears. He is last seen on one of the carts returning to Wall Rose, holding the badge in his left hand with his head down.
In the Battle of Shiganshina, as Erwin Smith begins to lament the dwindling hopes of his dream, Dieter stands among the many fallen Scout Regiment comrades in Erwin's mind, wanting to know if their deaths had meaning.