The purpose of this research is to determine the tendency toward self-harm and social identity among soldiers. In terms of purpose, the research is applied, and in terms of data collection methodology, it is a descriptive study from the branch of field studies, and regarding the relationship between research variables, it is correlational. The primary statistical population of this research consisted of soldiers serving in one of the military centers of Tehran. The inclusion criterion for the study was that the soldiers performed night guard duties. In this research, random sampling was used. The tool used was a questionnaire measured using a Likert scale. In this research, the items related to the social trust variable were obtained using Mobaraki's standardized questionnaire (2005/1384), and the items related to the tendency toward self-harm were adapted from Kit's suicide questionnaire (ASQ), along with library and documentary studies. In this research, SPSS19 software was used for data summarization and processing. Descriptive statistics (frequency and percentage) were used in univariate analyses. In bivariate analyses, Pearson's correlation test was used to examine the relationship between the social trust variable and self-harm. The results showed that there is a negative and significant relationship between these two variables (r=-0.339 and p=0.001); therefore, with an increase in social trust among soldiers, the tendency toward self-harm among them decreases.