Background: Deep neck infection (DNI) can progress to become a life-threatening complication. Liver cirrhosis, which is related to poor immune conditions, is a likely risk factor for DNI. This study investigated the risk and mortality of DNI in patients with decompensated liver cirrhosis (DLC). Methods: We performed a nationwide cohort study using the National Health Insurance Research Database (NHIRD) in Taiwan. We included a total of 33,175 patients with DLC between 2000 and 2013, from the Catastrophic Illness Patient Database, a subsection of the NHIRD, along with 33,175 patients without cirrhosis who were matched in a 1:1 proportion for age, sex, and socioeconomic status. The occurrence of DNI was the primary study outcome. The risk, treatment, and mortalities of DNI were evaluated in the study and comparison cohorts. Results: DLC Patients had a significantly higher incidence of DNI than noncirrhotic patients (p < 0.001). The adjusted Cox proportional hazard regression showed that DLC was associated with a significantly higher risk of DNI (adjusted hazard ratio, 4.11; 95% confidence interval, 3.16–5.35, p < 0.001). The mortality rate in cirrhotic patients with DNI was not significantly higher than that in noncirrhotic patients with DNI (11.6% vs. 9.8%; p = 0.651). Conclusions: This study is the first to investigate the correlation between DLC and DNI. The study findings strongly indicate that DLC is an independent risk factor for DNI. Cirrhotic patients with DNI do not have a significantly poorer survival rate than noncirrhotic patients with DNI. Therefore, physicians should be alert to potential DNI occurrence in DLC patients. Besides this, intensive care and appropriate surgical drainage can yield similar survival outcomes in DLC-DNI and noncirrhosis-DNI patients.