Background: Spontaneous fungal peritonitis (SFP) and fungiascites is less well-recognized and described in patients with liver cirrhosis. The aims of this study were to determine the clinical characteristics, prognosis, and risk factors of cirrhotic patients with SFP/fungiascites and to improve early differential diagnosis with spontaneous bacterial peritonitis (SBP). Methods: This was a retrospective case–control study of 54 cases of spontaneous peritonitis in cirrhotic patients (52 SFP and 2 fungiascites) with fungus-positive ascitic culture. Fifty-four SBP cirrhotic patients with bacteria-positive ascitic culture were randomly enrolled as a control group. A nomogram was developed for the early differential diagnosis of SFP and fungiascites. Results: Hospital-acquired infection was the main cause of SFP/fungiascites. Of the 54 SFP/fungiascites patients, 31 (57.41%) patients carried on with the antifungal treatment, which seemed to improve short-term (30-days) mortality but not long-term mortality. Septic shock and HCC were independent predictors of high 30-day mortality in SFP/fungiascites patients. We constructed a predictive nomogram model that included AKI/HRS, fever, (1,3)-β-D-glucan, and hospital-acquired infection markers for early differential diagnosis of SFP/fungiascites in cirrhotic patients with ascites from SBP, and the diagnostic performance was favorable, with an AUC of 0.930 (95% CI: 0.874–0.985). Conclusions: SFP/fungiascites was associated with high mortality. The nomogram established in this article is a useful tool for identifying SFP/fungiascites in SBP patients early. For patients with strongly suspected or confirmed SFP/fungiascites, timely antifungal therapy should be administered.