The paper examined effects of mood dysfunction and mal-behaviour and learning outcome of public secondary school students in Nigeria. It adopted the text content analysis in which literature and opinion were sought from journals, professionals contributions, internet and interviews with colleagues. The paper hinged its theory on Social learning theory which was developed by Albert Bandura and published in his 1977.  Every child or student wants to express their innate instincts and emotions naturally. Different types of social restrictions hinder the spontaneous manifestation of these innate instincts and emotions. Then they go against the students’ learning outcome. These unruly behaviours become a problem. These behaviours are also called maladjusted behaviour. These students or children can’t adjust to the society properly. This type of behaviour is most commonly seen among secondary level students. Such behaviours have a profound effect on their education. Therefore, it is very important to look for such behaviours and to find out the factors behind the behaviour. With that purpose we have sought to find out some of the maladjusted behaviours that affected the education of secondary level students in Nigeria. The paper concluded that mood disorder leads to mal-behaviour and suggested that frequent educational awareness to both students and parents should be carried out in order to reduce incidences of mood disorder and its attendant fall out effect of mal-behaviour.