The right to mental health is one of the main components of the right to health and one of the main examples of children’s rights. Various factors are influential in threatening or realizing this right of children including the cyberspace. Cyberspace is important as nowadays children spend a lot of time in it while a significant part of this space is not appropriate for the age and mental state of children as well it has a detrimental effect on their psyche. Using descriptive-analytical method, this study intends to answer this question that: How can the right to children's mental health in cyberspace be realized according to the Iranian legal system, Islam and international human rights instruments? To answer this question, different rights of children in cyberspace including the right to education, the right to privacy, the right to security and the right to play and recreation, and their relation with the right to mental health of children have been investigated. The results indicate that in the international human rights system, especially in protection of children’s right, some measures have been considered by the governments. In Islam, the health of people has been highly emphasized in the Quranic verses and hadith. However, in Iranian legal system, some measures have been taken to protect the mental health of children in cyberspace, but in practice, there are much to do to achieve the desired situation.