CDK12 (Cyclin-Dependent Kinase 12) is a serine/threonine kinase involved in transcriptional regulation, particularly in elongation and RNA processing. It plays a critical role in maintaining genomic stability by regulating the expression of DNA damage response (DDR) genes. Dysregulation of CDK12 is linked to cancers, including ovarian, prostate, and breast cancers, where its loss or mutation correlates with homologous recombination deficiency (HRD) and genomic instability. CDK12 antibodies are essential tools for studying its expression, localization, and function in both normal and pathological contexts. These antibodies are widely used in techniques like Western blotting, immunohistochemistry (IHC), and immunofluorescence (IF) to assess CDK12 protein levels in tissues or cell lines. Commercially available CDK12 antibodies are typically monoclonal or polyclonal, targeting specific epitopes within its kinase domain or C-terminal region. However, variability in antibody specificity has been noted, as some cross-react with homologous kinases like CDK13. Validating CDK12 antibodies using knockout controls is crucial for ensuring experimental accuracy. Recent studies highlight CDK12’s dual role in cancer progression and therapeutic resistance, making its antibodies valuable for biomarker research and targeted therapy development. Challenges remain in standardizing detection protocols due to tissue-specific expression patterns and post-translational modifications.