UNLABELLED: Length of stay (LOS) during index solid organ transplant impacts morbidity and healthcare costs. To date, there are no studies evaluating characteristics and outcomes of simultaneous liver-kidney transplant (SLKT) index hospitalization. We examined factors associated with LOS and mortality during index SLKT admission. METHODS: Adult SLKT recipients between 2002 and 2017 at 6 transplant centers across 6 UNOS regions were retrospectively enrolled in the US-Multicenter SLKT Consortium. Multivariable regression analyses assessed predictors of SLKT LOS and death during index admission. RESULTS: Median age of cohort (N = 570) was 58 y (interquartile range: 51-64); 63% male, 75% White, 32.3% hepatitis C, 23.3% alcohol-related, 20.1% nonalcoholic steatohepatitis with median MELD-Na at SLKT 28 (23-34). Seventy-one percent were hospitalized at the time of SLKT with median LOS pretransplant of 10 d. Majority of patients were discharged alive (N = 549; 96%)' and 36% were discharged to subacute rehab facility. LOS for index SLKT was 19 d (Q1: 10, Q3: 34 d). Female sex (P = 0.003), Black race (P = 0.02), advanced age (P = 0.007), ICU admission at time of SLKT (P = 0.03), high MELD-Na (P = 0.003), on cyclosporine during index hospitalization (P = 0.03), pre-SLKT dialysis (P < 0.001), and kidney delayed graft function (P < 0.001) were the recipient factors associated with prolonged LOS during index SLKT hospitalization. Prolonged LOS also contributed to overall mortality (HR = 1.007; P = 0.03). CONCLUSIONS: Despite excellent survival, index SLKT admission was associated with high-resource utilization with more than half the patients with LOS >2 wk and affected overall patient survival. Further investigation is needed to optimize healthcare resources for these patients in a financially strained healthcare landscape.