en Health Health Systematic Review <strong>Background: </strong>Nosocomial infections represent a serious public health concern worldwide, and, especially, in developing countries where, due to financial constraints, it is difficult to control infections. This study aimed to review and assess the prevalence of nosocomial infections in Iran.<br> <strong>&nbsp;&nbsp; Methods:</strong> Different databases were searched between January 2000 and December 2017. To determine the pooled prevalence, the stochastic DerSimonian-Laird model was used, computing the effect size with its 95% confidence interval. To examine the heterogeneity among studies, the I2 test were conducted.&nbsp; The reporting of observational studies in epidemiology (STROBE) checklist was used to assess the methodological quality of observational studies. To further investigate the source of heterogeneity, meta-regression analyses stratified by publication year, sample size and duration of hospitalization in the hospital were carried out.&nbsp;<br> <strong>&nbsp;&nbsp; Results:</strong> 52 studies were included. Based on the random-effects model, the overall prevalence of nosocomial infection in Iran was 4.5% [95% CI: 3.5 to 5.7] with a high, statistically significant heterogeneity (I2=99.82%). A sensitivity analysis was performed to ensure the stability results. After removing each study, results did not change. A cumulative meta-analysis of the included studies was performed based on year of publication and the results did not change. In the present study, a high rate of infections caused by Klebsiella pneumoniae (urinary tract, respiratory tract, and bloodstream infections) was found.<br> <strong>&nbsp;&nbsp; Conclusion:</strong> Preventing and reducing hospital infections can significantly impact on reducing mortality and health-related costs. Implementing ad hoc programs, such as training healthcare staff on admission to the hospital, may play an important role in reducing infections spreading.<br> &nbsp; Nosocomial infections, Prevalence, Iran, Systematic review, Meta-analysis, Hospital 273 282 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-2047-9&slc_lang=en&sid=1 Ahmad Ghashghaee Ghaemmohamadi.m@gmail.com 200319475328460039095 200319475328460039095 No Student Research Committee, Iran University of Medical Sciences, Tehran, Iran. Masoud Behzadifar masoudbehzadifar@gmail.com 200319475328460039096 200319475328460039096 Yes Health Management and Economics Research Center, Iran University of Medical Sciences, Tehran, Iran. Samad Azari samadazari1010@gmail.com 200319475328460039097 200319475328460039097 No Health Management and Economics Research Center, Iran University of Medical Sciences, Tehran, Iran. Zeynab Farhadi farhadi_zeynab@yahoo.com 200319475328460039098 200319475328460039098 No Babol University of Medical Sciences, Babol, Iran. Nicola Luigi Bragazzi robertobragazzi@gmail.com 200319475328460039099 200319475328460039099 No School of Public Health, Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy. Meysam Behzadifar m_behzadifar67@yahoo.com 200319475328460039100 200319475328460039100 No Social Determinants of Health Research Center, Lorestan University of Medical Sciences, Khorramabad, Iran & Department of Epidemiology, Faculty of Health & Nutrition, Lorestan University of Medical Sciences, Khorramabad, Iran. Sahar Sadat Saeedi Shahri s.s.saeedi75@gmail.com 200319475328460039101 200319475328460039101 No Student Research Committee, Iran University of Medical Sciences, Tehran, Iran. Mozhgan Sadat Ghaemmohamadi Ghaemmohamadi.m@gmail.com 200319475328460039102 200319475328460039102 No Student Research Committee, Iran University of Medical Sciences, Tehran, Iran. Faezeh Ebadi ebadi.faezeh@yahoo.com 200319475328460039103 200319475328460039103 No Student Research Committee, Iran University of Medical Sciences, Tehran, Iran. Roghayeh Mohammadibakhsh r.mohammadib@yahoo.com 200319475328460039104 200319475328460039104 No Department of Health Services Management, School of Health Management and In-formation Sciences, Iran University of Medical Sciences, Tehran, Iran. Hesam Seyedin h.seyedin@gmail.com 200319475328460039105 200319475328460039105 No Department of Health Services Management, School of Health Management and In-formation Sciences, Iran University of Medical Sciences, Tehran, Iran. Mahya Razi Moghadam 200319475328460039106 200319475328460039106 No Student Research Committee, Iran University of Medical Sciences, Tehran, Iran.