This review summarises current knowledge on the molecular “Ca2+ toolkit” in the human uterus, highlighting the role of voltage-gated calcium channels (VGCCs), transient receptor potential (TRP) channels, store-operated calcium entry (SOCE) components, Na+/Ca2+ exchangers, purinergic receptors, P-type ATPases (SERCA, SPCA, PMCA), ryanodine (RyR) and inositol 1,4,5-trisphosphate (IP3R) receptors, and mitochondrial Ca2+ uniporter (MCU) complexes in endometrial cancer progression. The gene discussed is SLC8A1; the disease is endometrial cancer.