Abstract Purpose: This prospective single-arm phase II clinical trial aimed to evaluate the efficacy and safety of pegylated liposomal doxorubicin (PLD) combined with ifosfamide (IFO) as the first-line treatment for patients with advanced or metastatic soft-tissue sarcoma (STS). Patients and Methods: Patients received PLD (30 mg/m2; day 1) in combination with IFO (1.8 g/m2; days 1–5) every 21 days until disease progression, unacceptable toxicities, patient death, or for up to six cycles. The primary endpoint was progression-free survival (PFS; NCT03268772). Results: Overall, 69 patients with chemotherapy-naïve advanced or metastatic STS were enrolled between May 2015 and November 2019. At a median follow-up of 47.2 months, the median PFS and overall survival (OS) were found to be 7.3 [95% confidence interval (CI): 5.7–8.9] and 20.6 (95% CI: 16.3–25.0) months, respectively. The response and disease control rates were 26.1% and 81.2%, respectively. Adverse events were manageable, and no grade 3–4 cardiotoxicities were observed. There was no significant change in left ventricular ejection fraction values between baseline and after treatment (P = 0.669). Exploratory biomarker analysis suggested NF1 single-nucleotide variant was associated with poor OS (P < 0.0001) and PFS (P = 0.044). In addition, 2 patients with BRCA2 loss progressed in the initial 2 months and died within 10 months. Improved OS was observed in homologous recombination deficiency (HRD)-negative patients compared with their HRD-positive counterparts (P = 0.0056). Conclusions: Combination therapy comprising PLD and IFO is an effective and well-tolerated first-line treatment for patients with advanced or metastatic STS.