Background: The signal peptide-CUB-EGF-like domain-containing protein 3 (SCUBE3) is a secretory protein that plays a role in cancer, cardiovascular, and immune disorders. SCUBE1, SCUBE2, and SCUBE3 belong to the SCUBE family. They contain multiple copies of EGF-like repeats at the amino acid terminal, a spacer region, three cysteine-rich motifs, and a CUB domain at the carboxyl terminus. The SCUBE family members are multifunctional proteins that act primarily as extracellular ligands or co-receptors in various cells. Methods: In this study, we examined the expression pattern and role of SCUBE3 in various cancers, as well as other diseases such as cardiovascular disease and immune disorders, and its impact on growth and development. Results: SCUBE3 expression is upregulated and secreted by the cells of lung cancer, hepatocellular carcinoma (HCC), melanoma, osteosarcoma, ovarian cancer, glioma, and breast cancer. Extracellular SCUBE3 protein often binds to TGFβRII or acts as a co-receptor for TGFβ and BMP2/BMP4 in regulating cellular signaling. Through the TGFβRII signaling, SCUBE3 activities promote tumor growth, metastasis, invasion, angiogenesis, and poor clinical outcomes. Conversely, in renal cell carcinoma, SCUBE3 expression suppresses growth. Altered SCUBE3 activity is associated with cardiovascular diseases, immune disorders, and hair growth. Conclusions: The review presents mechanistic evidence that SCUBE3 plays a crucial regulatory role in multiple cancers and other diseases. The evidence suggests the SCUBE3 protein could serve as a potential molecular target for various diseases and highlights its usefulness as a minimally invasive diagnostic marker, as it is a secreted protein.