Background <p>Multimorbidity (≥ 2 chronic conditions) is rising in aging populations. China reports over 80&#xa0;million surgeries annually. This study investigates health burdens of multimorbidity in Chinese surgical patients. It highlights its impact on postoperative outcomes using large-scale data across diverse surgical types, addressing a key gap in existing evidence.</p> Methods <p>This retrospective cohort study includes adult patients who underwent non-cardiac surgery in 2023 at a major national-level medical center in China. Patients were categorized by having no morbidity, one morbidity, or multimorbidity. Outcomes included in-hospital mortality, hospital stay, and hospitalization costs. Multivariable regression analyses assessed associations, and identified disease combinations with the highest risk and costs.</p> Results <p>Among 37,084 surgical patients, 17.4% had multimorbidity. Their in-hospital mortality rate was 1.5%, compared to 0.7% with one morbidity and 0.2% with none. Median hospital stays were 8, 7, and 6 days, respectively. Patients with multimorbidity had higher median hospitalization costs ($6,485), compared to $4,975 for one morbidity, and $3,714 for none. Multivariable analysis demonstrated multimorbidity was significantly associated with higher postoperative mortality (<i>P</i> &lt; 0.001), longer hospital stays (<i>P</i> &lt; 0.001), and increased cost (<i>P</i> &lt; 0.001). Hypertension combined with chronic kidney disease and anemia posed the highest mortality risk and costs.</p> Conclusions <p>Multimorbidity was linked to a 2 to 7-fold increase in mortality, 1–2 extra hospital days, and $1,510–2,771 higher costs compared with patients having one or no morbidities. This large-scale annual study in China underscores the need for enhanced preoperative evaluations and tailored care strategies to improve outcomes and reduce costs for multimorbid surgical patients.</p>