Objective: To describe imaging and clinical features of primary mesenchymal chondrosarcoma (MCS) and evaluate for presence of a distinct biphasic pattern on imaging. Material and methods: Patients with a pathologic diagnosis of MCS were identified along with imaging of their primary tumor. Size, location, appearance (lytic, sclerotic, or mixed), presence, extent and distribution of calcifications, cortical destruction, soft tissue extension, periosteal reaction, contrast enhancement, and radiotracer uptake were recorded. The presence of T2-hyperintense tumor lobules on MRI and a biphasic morphology (distinct calcified and non-calcified components) on CT were assessed. Presence and location of metastases were documented. Results: Twenty-three patients (mean age 28.0 ± 13.8 years) were reviewed (13 skeletal, 10 extraskeletal). Overall mean tumor size was 10.2 ± 7.2 cm, 7.1 ± 7.3 cm in non-metastatic and 13.2 ± 5.9 cm (p = 0.004) in metastatic cases. Locations were extremities (n = 11), head/neck (n = 4), chest wall (n = 4), pelvis (n = 3), and retroperitoneum (n = 1). Skeletal MCS were aggressive mixed lytic and sclerotic (n = 8), purely lytic (n = 4), or juxtacortical (n = 1) lesions with cortical destruction and soft tissue extension. Chondroid calcifications were common (80%). On MRI, the presence of T2-hyperintense lobules was seen in 35%. A biphasic morphology on imaging was seen in 30%. Metastases were common (52%) with the most common site being the lungs (75%). All tumors were hypermetabolic with a mean SUVmax of 14.3 (5.6–34) on PET/CT. Conclusion: Skeletal MCS commonly present as aggressive lytic bone lesions with chondroid calcifications. A biphasic morphology was seen in one-third of cases. Metastases were common at initial presentation and more commonly seen with larger tumors. [ABSTRACT FROM AUTHOR]