Patients with mental health disorders often have to endure the burdens of the condition itself and the stigma that follows. Since no study has been conducted in Lebanon on this topic, our objective was to assess the knowledge, attitude and behaviors towards public stigma of mental health diseases, among a sample of the Lebanese population.A cross-sectional study, conducted between November 2017 and May 2018, enrolled 2289 participants. The Mental Health Knowledge Schedule (MAKS), the Community Attitudes toward Mental Illness (CAMI) and the Reported and Intended Behavior Scale (RIBS) were used to assess knowledge, attitude and behaviors toward mental illness respectively. The 25th, 50th and 75th percentile of the MAKS, CAMI and RIBS scales scores were considered as cutoff points for low, medium and high scores respectively.A high knowledge score was found in 33.0% of the participants, whereas a high attitude score and a higher behavior score were found in 32.2% and 26.9% of the participants respectively. Living in North Lebanon (Beta = 1.331) and being familiar with a non-close person with mental illness (Beta = 0.811) were associated with higher knowledge of mental illness (higher MAKS score), whereas living in Bekaa (Beta = -8.693) and being 70 years old and above (Beta = -5.060) were associated with lower knowledge toward mental illness (lower MAKS score). Higher knowledge of mental illness (higher MAKS score) (Beta = 0.670), having a high level of education (university (Beta = 8.785), secondary (Beta = 6.084) and technical (Beta = 5.677)) were associated with less stigmatizing attitudes (higher CAMI scale). Being familiar with close people with mental illness (Beta = 0.577), less stigmatizing attitudes (higher CAMI scale) (Beta = 0.077) and higher knowledge of mental illness (higher MAKS score) (Beta = 0.115) were associated with higher favorable behaviors (higher RIBS score), whereas knowing a non-close person who have a mental illness (Beta = -0.720) was associated with lower favorable behaviors (lower RIBS score).A mass media awareness campaigns that could transmit health messages to a wide public audience in the country to fight stigma toward mental illness, seems warranted.