Background Determination of preoperative soft tissue sarcoma (STS) margin is crucial for patient prognosis. Purpose To evaluate diagnostic performance of radiomics model using T2‐weighted Dixon sequence for infiltration degree of STS margin. Study Type Retrospective. Population Seventy‐two STS patients consisted of training (n = 58) and test (n = 14) sets. Field Strength/Sequence A 3.0 T; T2‐weighted Dixon images. Assessment Pathologic result of marginal infiltration in STS (circumscribed margin; n = 27, group 1, focally infiltrative margin; n = 31, group 2‐A, diffusely infiltrative margin; n = 14, group 2‐B) was the reference standard. Radiomic volume and shape (VS) and other (T2) features were extracted from entire tumor volume and margin, respectively. Twelve radiomics models were generated using four combinations of classifier algorithms (R, SR, LR, LSR) and three different inputs (VS, T2, VS + T2 VST2 features) to differentiate the three groups. Three radiologists (reader 1, 2, 3) analyzed the marginal infiltration with 6–scale confidence score. Statistical Tests Area under the receiver operating characteristic curve (AUC) and concordance rate. Results Averaged AUCs of R, SR, LR, LSR models were 0.438, 0.466, 0.438, 0.466 using VS features, 0.596, 0.584, 0.814, 0.815 using T2 features, and 0.581, 0.587, 0.821, 0.821 using VST2 features, respectively. The LR and LSR models constructed with T2 or VST2 features showed higher AUC and concordance rate compared to radiologists' analysis (AUC; 0.730, 0.675, 0.706, concordance rate; 0.46, 0.43, 0.47 in reader 1, 2, 3). Data Conclusion Radiomics model constructed with features from tumor margin on T2‐weighted Dixon sequence is a promising method for differentiating infiltration degree of STS margin. Evidence Level 4 Technical Efficacy Stage 2