While economic deterrence models are fully based on maximizing economic utility; social psychology models explain human behavior by examining the underlying attitudes, norms and beliefs. Tax morale is defined as the intrinsic motivation to pay taxes. However, determinants of tax morale need to be investigated for a more comprehensive understanding of tax morale. In this paper we analyze the most important determinants of tax morale in Iran using data from World Values Surveys (WVS). Determinants of tax morale are categorized into four main groups: social capital, conditional cooperation, demographic factors and economic situation of the respondents. Estimating ordered probit model, we find that conditional cooperation and economic situation have the most important effects on tax morality. However, some of the social capital variables like importance of politics and religion and demographic factors like gender and marital status don’t have significant effect on tax morale in Iran.