Background: Many Nigerians have misconceptions and misbeliefs about mental illness, hence stigmatize people with mental illness. This scoping review on the knowledge of and attitude towards mental illness among Nigerians aims to identify the extent of literature on the issue, summarize current reports and identify research gaps in hopes to proffer workable solutions to this problem. Methods: A scoping review was designed to identify peer-reviewed articles only. Key search terms with synonyms were pre-developed and mapped on six bibliographic databases; Medline/Pubmed, Scopus, Web of knowledge, Embase, PsycINFO, and PsychARTICLES. No grey literature searches and no time line restrictions were observed. Results: Twenty five articles met the eligibility criteria and were selected for scoping out of a total of 2079 identified articles (2063 from the library databases and 16 from hand searching of article citations). Most studies were qualitative (23/25;95%) and some mixed (2/25; 8%). Study designs observed in the scoping articles were cross-sectional studies (24/25; 96%) and community-based research (1/25; 4%). Most common knowledge of causes of mental illness observed in scoping articles was supernatural causes (magic, witchcrafts, sorcery, and divine punishments). Social distance was the most common attitude expressed in articles scoped and traditional (unorthodox) medicine was a treatment preference in reference to health seeking behaviours. Conclusion: In a country like Nigeria, where poor mental health facilities, poor health outcomes, health inequalities and disparities exist, the need for mental health literacy, and workable health policies are vital. These will significantly reduce stigma and increase health seeking behavior of the mentally ill.