Granulin (GRN) antibodies are immunological tools targeting progranulin, a multifunctional glycoprotein encoded by the *GRN* gene. Progranulin is involved in diverse cellular processes, including inflammation, wound repair, lysosomal function, and neuronal survival. It is expressed in various tissues, particularly immune cells, neurons, and epithelial cells. Dysregulation of progranulin is linked to neurodegenerative diseases, notably frontotemporal dementia (FTD) caused by *GRN* loss-of-function mutations. These mutations lead to haploinsufficiency, reducing progranulin levels by ~50%, which promotes TDP-43 proteinopathy and neurodegeneration. GRN antibodies are critical in research to quantify progranulin in biological samples (e.g., plasma, CSF) for diagnosing *GRN*-associated FTD or monitoring therapeutic interventions. They also help study progranulin's role in lysosomal biology and neuroinflammation. Additionally, progranulin’s dual role in cancer—acting as a growth factor in some tumors while suppressing others—has spurred interest in GRN antibodies for oncology research. Commercially available GRN antibodies include monoclonal and polyclonal variants, validated for techniques like ELISA, Western blot, and immunohistochemistry. Challenges remain in ensuring antibody specificity due to progranulin’s complex structure (containing 7.5 granulin domains) and cross-reactivity with related proteins. Ongoing research aims to refine these tools for clinical and mechanistic studies.