Objective The correlation between happiness and health is well established. This study aimed to measure happiness and its correlates among a sample of young adults in Iran. As such a national cross sectional study was conducted and the Oxford Happiness Questionnaire (OHQ) was administered to measure happiness. We performed logistic regression analysis to examine the relationship between happiness and independent variables. Results In all 14292 young adults (7702 female and 6590 male) were completed the questionnaire. The mean happiness score for the study sample was 4.09 (SD = 0.57) out of 6; indicative of a condition that is named as ‘rather happy; pretty happy’. The results obtained from multiple logistic regression analysis showed insignificant association between happiness, age, gender, and education whereas the association between happiness and income [OR for poor/very poor= 1.69, 95% CI: 1.51-1.90] and employment status [OR for unemployed = 1.88, 95% CI: 1.53-2.32] was significant. In addition separate analyses for men and women showed that income and employment still were significant for men but for women only income was significant.