Background Studies on the epidemiology of sepsis in intensive care units (ICUs) of prefecture-level hospitals in China are rare. This study aimed to investigate the epidemiological characteristics and mortality risk factors of sepsis in ICUs of tertiary hospitals in Sichuan, China. Material/Methods In this prospective, multicenter, observational study, patients admitted to the ICU of 7 tertiary hospitals in Sichuan (China) between October 10, 2017 and January 9, 2018 were screened for sepsis using the Sepsis-3 criteria. Patients with sepsis were included. Results Of the 1604 patients screened for sepsis, 294 (18.3%) had sepsis, and 140 (47.6%) had septic shock. Of these, 169 (57.5%) died. Multivariable analysis showed that central nervous system dysfunction (odds ratio [OR]=2.59, 95% confidence interval [CI]: 1.15–5.84, P=0.022), lowest blood phosphorus level (OR=2.56, 95% CI: 1.21–5.44, P=0.014), highest lactate level (OR=1.20, 95% CI: 1.10–1.32, P<0.001), 24-h Acute Physiologic Assessment and Chronic Health Evaluation-II (APACHE-II) score (OR=1.08, 95% CI: 1.03–1.13, P=0.002), and lung infection (OR=2.57, 95% CI: 1.30–5.09, P=0.007) were independently associated with mortality in patients with sepsis. Conclusions The prevalence and mortality rates of sepsis are high in tertiary hospital ICUs in Sichuan, China. The APACHE-II score on day 1 after diagnosis, acute central nervous system dysfunction, lowest blood phosphorus, high serum lactate, and lung infection were independent risk factors of mortality in patients with sepsis.