In contemporary Greek history we do not encounter the historical and social phenomena of colonialism or post-colonialism with the exception of cases where nations conquered Greek islands; the Dodecanese Islands and the Eptanisa (Seven Islands) were conquered by the English and the Italians, and Cyprus was conquered by the British in the Middle Ages and in contemporary times. These historical situations have been transferred into certain historical Greek fictions in adult literature and in the literature of children and young adult. The focus of this essay is on investigating and depicting colonialist attitudes and post-colonialist situations in science fiction for Greek Children. Initially, we attempt a brief introduction to the literature of children and young adults and mainly science fiction for children in Greece, and following this we outline the aims of our research. Then we define the terms “colonialism,” “postcolonialism” and the new suggested terms “historical colonialism” and “literary colonialism” and refer to their relationship with science fiction. This is due to the fact that the setting of these narratives “is dictated” by a group of events that the writers themselves have either brought about or believe will take place in the future. Afterwards we point out the criteria that are used to distinguish between five types of colonization in the texts and we investigate at greater length the role that children and adolescents play in the texts, as they participate actively as liberators and saviors, as protectors for peace and the environment or as characters that take on the roles of adults. The children and young adults remain passive spectators of a peaceful colonization or do not participate in the action since the heroes in the story are insects. In this case, they are limited to the role of reader. Through the study of these texts, we detect similarities to similar situations, both in antiquity and at a later date, or during contemporary times where similar policies in certain countries have been regarded. Finally, we realize that after the inversion of colonialism and the liberation of the colonized planets, these planets are governed democratically, according to Plato’s and Aristotle’s ideas on politics.