Theater is a process that helps participants in the process of purposeful communication to recreate social and psychological issues in a real context, not just talk about them. On the other hand, happiness includes different physical and mental states of human beings, which leads to a feeling of satisfaction and more energy in the audience. The present research aimed to investigate the relationship between watching theater and social vitality among the citizens of Yazd city was carried out by a descriptive method of correlation type. To determine the sample size, Krejcie and Morgan’s table with an unlimited approach was used, and according to the statistics presented in this table, the sample size for the unlimited population is considered to be 384 people. The sampling method in this study was cluster sampling. To collect data, the 29-question Oxford Happiness Questionnaire (2002) and the 14-question theater viewing questionnaire by Karim-Vand and Ahmadi (2015) were used. The content validity of the questionnaires was confirmed by the supervisor and 10 subject matter experts, and the face validity of the questionnaire was confirmed by several members of the statistical community. The reliability of the questionnaires was calculated using Cronbach’s alpha for the happiness questionnaire of 0.899 and the theater viewing questionnaire of 0.838. The results of the research showed that there is a difference between watching theater with social vitality among the citizens of Yazd city (r=0.742), between liveness of theater and social vitality (r=0.693), between honesty and lack of censorship in theater with social vitality (r=0.656), between the unique features of theater with social vitality (r=0.709), between the specificity of the audience of theater with social vitality (r=0.472) and between the motivation and need for theater with social vitality (r=0.368), Genre and content of theater (r=0.556), visual elements (r=0.467) and non-visual elements (r=0.682) is significant at the significance level of 0.05. The results of the research showed the correlation coefficient between watching theater with (components of liveness of theater, honesty and non-censorship of theater, unique characteristics of theater, specificity of audience, motivation and need for theater) with social vitality based on (components of life satisfaction, contentment, self-respect, positive mood, positive energy) there is a positive and meaningful relationship.