Introduction: Physical and mental health are the most important indicators of development and prosperity of any society and  public libraries have a key role in disseminating  information. This study investigates the impact of the public libraries under the auspices cultural organization of Tehran Municipality on mental health of the users.

Methods: This is a 2015 cross-sectional study. The study population consisted of public library users in Tehran under the auspices of Culture and Art Organization of Tehran. Based on cluster sampling, 233 samples from North, South, East and West of Tehran were randomly selected. The Questionnaire developed by the researchers was distributed among library users. Descriptive statistics (mean, standard deviation) and inferential statistics (test T) in SPSS software version 21 was used for data analysis.

Results: The Results showed public libraries with the mean of 3.10 will affect the mental health of its users, also in the area of social welfare and emotional well-being the impact was 2.80 and 3.07 respectively.  The mean of mental, social welfare, and emotional wellbeing domains were not significantly different between men and women.

Conclusion: The results showed that although the mean score in components of mental health was average but mostly it is inclined towards below the average, hence we can conclude that public libraries do not have a strong effect on the mental health of their users , therefore the  need for the libraries to revise their policies and  performance to be more appealing to the users is felt.