Soft-tissue sarcomas during infancy are rare and understudied. With no data on this specific condition, we performed a retrospective study of infant-onset sarcomas based on a multi-institutional cohort in Beijing, China, collected over the past decade. We reviewed infantile soft-tissue sarcomas' clinical characteristics, treatments, and outcomes.The patients with soft-tissue sarcoma diagnosed from 0 to 12 months in four primary children's hospitals in Beijing from January 2010 to December 2019 were evaluated.Fifty-one patients were enrolled, including 31 males and 20 females. The median age at the diagnosis was five months (range, 0-12), and seven (13.7%) patients were diagnosed in the first month of their life. Histologically, twenty-five patients were diagnosed with rhabdomyosarcoma (RMS), six were diagnosed with extraosseous Ewing sarcoma (EES), and twenty were diagnosed with nonrhabdomyosarcoma soft-tissue sarcoma (NRSTS). The treatment principles and details of RMS focused on reference to the Intergroup Rhabdomyosarcoma Study Group (IRSG) protocols. For EES and NRSTS, chemotherapy was prescribed according to children's oncology group protocols. The five-year EFS/OS rates of RMS were 26.4% ± 19.5%/56.2 ± 17.8%, the five-year EFS/OS rate of EES was 50% ± 20.4%, and the five-year EFS/OS of NRSTS was 85.2% ± 9.8%/100%.Infant-onset soft-tissue sarcoma is heterogeneous. The primary location of the abdominal or pelvic cavity of RMS and EWS was at a later stage and had a poorer prognosis. Multimodal therapy resulted in successful disease control for the majority of patients. Standardization of treatment protocols will facilitate care for such challenging conditions.