Importance Dermatomyositis (DM) is associated with increased rates of hospitalization and mortality. However, characteristics present at the time of admission that are associated with in-hospital mortality remain poorly defined in the US. Objective To evaluate whether features of DM present at admission, including active rash and muscle disease, interstitial lung disease (ILD), elevated neutrophil to lymphocyte ratio (NLR), myositis-specific autoantibody status, and baseline treatment regimens, are associated with in-hospital mortality among patients admitted with DM. Design, Setting, and Participants This cohort study included adults with pre-existing DM (confirmed by documentation by a dermatologist or rheumatologist) who were admitted for any cause at a single tertiary referral center from January 2013 to May 2024. Data were analyzed from August 2024 to August 2025. Exposures Clinical, serologic, and laboratory features of DM at the time of admission as well as baseline treatment prior to hospitalization. Main Outcomes and Measures The primary outcome was in-hospital mortality. Statistical analyses included descriptive statistics and multivariable logistic regression with the Firth correction, adjusting for demographics and DM subtype. Bonferroni correction was applied to control for multiple comparisons. Results Among 153 patients with DM (113 females [73.9%]; mean [SD] age, 56.5 [14.3] years), 16 (10.5%) died during hospitalization. Deceased patients were more likely than survivors to have active rash (13 of 16 [81.3%] vs 47 of 137 [34.3%]), ILD (14 of 16 [87.5%] vs 57 of 137 [41.6%]), and elevated NLR (mean [SD], 12.5 [7.43] vs 4.90 [3.82]). Myositis prevalence did not differ significantly between deceased patients and survivors. In multivariable analysis, active rash (odds ratio [OR], 12.13; 95% CI, 3.18-46.28; P = .003), ILD (OR, 6.43; 95% CI, 1.78-23.13; P = .04), and NLR (OR per 1-unit increase, 1.29 [95% CI, 1.16-1.44]; P &lt; .001) were independently associated with mortality. No association with baseline intravenous immunoglobulin use was observed among patients who died after Bonferroni correction. Conclusions and Relevance In this study, active rash, ILD, and elevated NLR were independently associated with in-hospital mortality in patients with DM, regardless of disease subtype or myositis-specific autoantibody status. Recognizing these high-risk features may guide inpatient management and support future risk stratification strategies.