This research examines the main characters’ sadism in the collection of fairy tales Der Struwwelpeter by Heinrich Hoffmann. It aims to describe (1) the main characters’ sadism and (2) the causes of the main characters’ sadism in Heinrich Hoffmann's fairy tales. A qualitative approach was applied to conduct this research. The data sources were the fairy tales entitled Die gar traurige Geschichte mit dem Feuerzeug, Die Geschichte vom Daumenlutscher, and Die Geschichte vom bösen Friederich in the collection of fairy tales Der Struwwelpeter by Heinrich Hoffmann. This study applied the sadism theory by Erich Fromm (2000) to identify the main characters’ sadism and the aggression theory by Sears (1994) and Myers (2012) to analyze the main characters’ motives for doing the sadism. The results reveal six data which show kinds of sadism and seven data of the causes. Two data prove the main characters’ sadism in each fairy tale. Four data regarding the causes of sadism are found in Die gar traurige Geschichte mit dem Feuerzeug. Other two similar data are found in Die Geschichte vom Daumenlutscher and the other one in Die Geschichte vom bösen Friederich. In conclusion, sadism in the three of Heinrich Hoffmann’s fairy tales is described as non-sexual (physical) sadism, while the type of sexual and sadism is not found. Moreover, the motives of the main character in the Die gar traurige Geschichte mit dem Feuerzeug are caused by observation and imitation of other people’s activities. The main character’s biological factor is the motive in the Die Geschichte vom Daumenlutscher and Die Geshichte vome bösen Friederich. There are two similarities found in these three fairy tales: non-sexual (physical) sadism acted by the main characters and instrumental aggression as the type of aggression. 
