AbstractBackgroundHappiness has multiple levels and determinants in different communities, cultures, and social groups. The current study aimed to investigate happiness and its main determinants in slums in south central Iran.MethodsThis community-based, cross-sectional study was conducted with the participation of adults at least 18 years of age living in the biggest slum area in Shiraz, south central Iran. To determine levels of happiness, participants were asked to complete the Persian version of the GHQ28 questionnaire and a checklist based on the 2017 World Happiness Report. Data was analyzed using SPSS software version 19. Ap-value less than 0.05 was considered significant.ResultsThe mean age of the participants was 42.06 ± 16.34 years. Overall, 542 participants (45 %) were females, 257 (21.3 %) were illiterate, 678 (56.3 %) were married, and 495 (41.1 %) were unemployed and lived with their household. The happiness score, according to the Cantril ladder score, was 6.41 ± 2 (out of a total score of 10). Happiness was not correlated with gender (p = 0.37) or immigration (p = 0.06). Lower levels of happiness were seen in older adults (r=− 0.12,p < 0.001), illiterates (p = 0.03), the unemployed (p < 0.001), and people separated from their spouses (p < 0.001). Job satisfaction (p < 0.001, r = 0.47), total general health (p < 0.001, r=-0.36) and hope (p < 0.001, r = 0.41) were significantly correlated with happiness. Social support (< 0.001) and sufficient income and satisfaction (p < 0.001) were related with a higher score of happiness.ConclusionsMarital status, smoking, employment and job satisfaction, social support and trust, feelings of insecurity in the neighborhood, hope for the future, facing violence, and income satisfaction were the main determinants of happiness in the Sang Siah slum area.