Purpose This study primarily aims to evaluate the mental health literacy (MHL) of the Lebanese adult population in an attempt to yield results that can help fill the gap in the literature and support the development of new strategies to counter mental health stigma. Design/methodology/approach A cross-sectional survey was composed of the Mental Health Knowledge Schedule and select questions from the Community Attitudes toward the Mentally Ill and MHL Scale. The surveys were collected from a representative population of sample size (n = 386) among the different governorates of Lebanon. The participants, aged 18–65 years and literate, were recruited between July 2018 and September 2018 from supermarkets widely distributed across the country. Findings The results showed that the Lebanese population possesses average knowledge and certain stigmatizing attitudes toward mental illnesses. Curricular education and awareness campaigns may help refine the image of mental illness among the population. Originality/value To the best of the authors’ knowledge, this paper is one of the first in Lebanon to assess the MHL of its population as a whole. It gives insight into the common misconceptions about mental illness and patterns of the related stigma that are prevalent in the Lebanese society today.