Although a city has to have certain physical characteristics to be considered as developed, but attention should also be paid to the mental and social needs of the residents and that the citizens should be energetic, dynamic and cheerful. University is a modern institution and the place of modern institution is city. Students, as an effective and important stratum, can act as the engine for happiness in city. Therefore, the aim of present research is to study the amount of happiness among students in Yazd University and to see what factors affect it. The method of research was survey and the research population consisted of Yazd university students in second term of academic year of 1389. The sample included 277 students (154 girls & 123 bots) that were selected via stratified sampling. The main technique of gathering data was questionnaire which had appropriate level of validity and reliability. The data analysis techniques were Pearson correlation, T- test, one way variance analysis & stepwise multiple regression. The results showed that the mean score of happiness were between 42±46 that congruent with the score of happiness in developing countries. There were no significant relationships between the amount of happiness and variables like age, sex, marital status, the place of residence, education. But the relationship between happiness and field of study was significant. Pearson's correlation showed that social happiness was significantly related to religiosity, the use of mass media, hopefulness about future, and self-esteem. The regression analysis also showed that the three variables of self-esteem, hopefulness about future, and religiosity explained about 44.8 percent of variance of the dependent variable.