Uterine fibroids (UFs) are the most common benign gynecologic tumours affecting women of reproductive age. This study aims to deepen the understanding of UFs complex aetiology through harnessing the power of 3D organoid models derived from human myometrial stem cells to emulate the in vivo behaviour of these tumours. Isolated SCs were cultured over 7 days under a defined culture system. Immunohistochemistry, Immunofluorescence, organoid stiffness, RNA Sequencing was conducted, and differential gene expression was assessed using RT-PCR. The derived organoids exhibited diverse populations of cells, including stem cells, smooth muscle, and fibroblasts. Excessive ECM deposition was shown via Collagen and Fibronectin expression. We confirmed that our organoids expressed oestrogen receptor in a pattern similar to that in their corresponding tissue, as well as responded to steroid hormone. Interestingly, we revealed significant racial disparities in ECM accumulation within organoids derived from different racial groups. This augmented ECM deposition is theorised to enhance tissue stiffness, as assessed using Young's modulus. Additionally, our research demonstrated significant decreases in fibrotic markers upon treatment with Vitamin D3 and Doxercalciferol. Furthermore, the pro-fibroid effects of environmental phthalates further elucidate the potential factors contributing to UF pathology. The 3D organoid model can serve as a robust platform to study the underlying molecular mechanisms of UFs, besides offering invaluable insights for potential therapeutic interventions.