Social justice is among the concepts that have always been accompanied by the original thoughts of humanity. Despite all the differences of opinion in this matter, it has been endowed with spiritual value. Ayatollah Mutahhari's perspective on justice is based on his theory of human nature (fitrah), which influenced his approach to various fields, including law, jurisprudence and political philosophy. According to his attitude, Islamic rules are based on rational goodness and badness. Consequently, right and justice are real. In fact, this attitude demonstrates the foundations of Islamic law. Two things create connection between right and possessor of right: ultimate causality (which creates potential rights and the root of natural equal rights among individuals) and effective causality (which creates actual rights and the root of different acquired rights in individuals). The reliance of social justice on fitrah has also provided the grounds for raising issues such as global justice and inter-generational justice. Among the valuable points of the theory of natural justice, which have been discussed by prominent philosophers, is the idea of a Utopia city in which natural justice is a central point, i.e. is the cause of society's progression in both material and spiritual aspects by providing the groundwork for the realization of natural talents of the individual and society. In other words, natural justice provides a fair competition ground and opportunities for all members of society to freely compete in developing their inherent talents. In this article, the theory of justice based on fitrah is examined.