Background: Happiness, a factor in social, political, and economic development, leads to higher performance, increase in production, and great efficiency. The goal of this study was to assess the level of happiness in Iran's work communities.Methods: In this cross-sectional survey study, we randomly selected 13842 people from 380 workplaces in 31 provinces of Iran. Trained interviewers based on structured questionnaires collected data. Reliability of the questionnaire determined by using internal consistency. Collected data were analyzed through SPSS 16 software (SPSS Inc., Chicago, IL) and the charts and tables were prepared to indicate each province's happiness level and the national mean.Results: Average age of employees was 35.4±7.78 years. The majority of the respondents were male(n=11835, 85.5%), had finished middle/secondary school (n=7142, 51.6%) and were married (n=11323, 81.8%). The level of happiness varied from the highest value 148.97±21.49 in Boushehr Province and the lowest 130.39± 25.28 in Hormozgan Province. The mean ± SD value of happiness in the work communities of Iran was 141.22±22.89. Conclusion:Policymakers should consider workers' happiness as an effective factor in production and efficiency.