Background: Although elderly patients (≥70 years) represent 30% of new diagnoses of soft tissue sarcoma (STS), they are underrepresented in clinical trials and are often unfit to receive standard anthracycline-based chemotherapy. Trabectedin is registered as a second-line treatment for advanced STS and is characterized by a favorable safety profile. Methods: The aim of this single-arm, phase 2 study was to investigate trabectedin (scheduled dose, 1.3-1.5 mg/m2) as a first-line treatment in elderly patients with advanced stage STS who are inoperable and are unfit to receive standard anthracycline-based chemotherapy. The coprimary endpoints were progression-free survival at 3 months (PFS3) and the rate of clinically limiting toxicities (CLTs). We also conducted an ancillary study on pharmacokinetics. Results: Twenty-four patients (12 men and 12 women) with a median age of 79 years (interquartile range [IQR], 74-83 years) were enrolled. The histological subtype was leiomyosarcoma in 46%, liposarcoma in 33%, and other histotypes in 21%. The median number of trabectedin courses was 4 (IQR, 3-6), with 7 patients (29%) receiving ≥6 cycles. Eight patients (33%) required dose reductions. The most frequent grade 3/4 adverse events were neutropenia in 9 patients (38%), fatigue in 5 patients (21%), and aminotransferase elevation in 5 patients (21%). PFS3, median PFS, and overall survival were 71% (80% CI, 57%-81%), 4 months, and 12 months, respectively. Ten patients (42% [80% CI, 28%-57%]) experienced CLTs. Trabectedin Cmax, half-life, clearance, and distribution volume were 1.28 ng/mL (standard deviation [SD], 0.58 ng/mL), 26.70 hours (SD, 9.09 hours), 39.98 L/h/m2 (SD, 14.08 L/h/m2), and 1460 L/m2 (SD, 561 L/m2), respectively. Conclusion: Trabectedin can be administered safely to elderly patients with STS who are unfit to receive anthracyclines. Pharmacokinetics in the elderly population was superimposable to historical data.