Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 48 12 2019 12 02 2277 2284 Elahe FALLAHTAFTI Department of Counseling, Faculty of Educational Sciences and Psychology, Shahid Beheshti University, Tehran, Iran Meisam NASEHI Department of Biology, Faculty of Basic Sciences and Technologies, Science and Culture University, Tehran, Iran Roya RASULI Department of Counseling, Faculty of Educational Sciences and Psychology, Alzahra University, Tehran, Iran Dariush D. FARHUD School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Taghi POUREBRAHIM Department of Counseling, Faculty of Educational Sciences and Psychology, Shahid Beheshti University, Tehran, Iran Hassan ZAREEEIMAHMOODABADI Department of Psychology, Faculty of Educational Sciences and Psychology, Yazd University, Yazd, Iran 2019 12 02 Background: Sex is one of the major social classes in any society. Gender identity as the most fundamental element of human life from beginning to end. While most people with behavior and attitudes appropriate to their physiological gender, but among them are also those sexual behaviors with their physical sex does not match, that say to this group transsexual people. The aim of this study was to investigate happiness and mental health in transsexual individuals before surgery and after surgery. Methods: This quasi-experimental study, consisted of 42 patients before surgery and after surgery inside Iran in 2016-2017. Snowball sampling method was selected. The instrument was Oxford Happiness Questionnaire (OHQ) and Symptom Check List (SCL25). Data were analyzed using SPSS, t-test independent groups and one-way ANOVA. Results: There was significant difference between transsexual individuals before surgery and after surgery in mean score of happiness (P<0.01) (t=-4/84). Moreover, there was significant difference between the two groups in mean score of mental health (P<0.01) (f=19/13). Conclusion: Transsexual individuals after surgery experienced more happiness and mental health than those before surgery. https://ijph.tums.ac.ir/index.php/ijph/article/view/19083 https://ijph.tums.ac.ir/index.php/ijph/article/download/19083/6611