Objectives: Patients with connective tissue diseases (CTD) such as systemic lupus erythematosus (SLE) have an increased risk for infections. This study investigated the outcome and characteristics of CTD patients under intensive care unit (ICU) treatment for sepsis. Methods: A single-center retrospective analysis was conducted and reviewed all patients with a CTD diagnosis admitted to the ICU of a university hospital for sepsis between 2006 and 2019. Mortality was computed and multivariate logistic regression was used to detect independent risk factors for sepsis mortality. Furthermore, the positive predictive value of ICU scores such as Sequential Organ Failure Assessment (SOFA) score was evaluated. Results: This study included 44 patients with CTD (mean age 59.8 ± 16.1 years, 68.2% females), most of them with a diagnosed SLE (61.4%) followed by systemic sclerosis (15.9%). 56.8% (n = 25) were treated with immunosuppressives and 81.8% (n = 36) received glucocorticoids. Rituximab was used in 3 patients (6.8%). The hospital mortality of septic CTD patients was high with 40.9%. It was highest among systemic sclerosis (SSc) patients (85.7%). SOFA score and diagnosis of SSc were independently associated with mortality in multivariate logistic regression ( P = 0.004 and 0.03, respectively). The Simplified Acute Physiology Score II (SAPS II), SOFA and Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were good predictors of sepsis mortality in the investigated cohort (SAPS II AUC 0.772, P = 0.002; SOFA AUC 0.756, P = 0.004; APACHE II AUC 0.741, P = 0.007). Conclusions: In-hospital sepsis mortality is high in CTD patients. SSc diagnoses and SOFA were independently associated with mortality. Additionally, common ICU scores were good predictors for mortality.