CDK11A and CDK11B, encoded by the homologous genes *CDK11A* (also known as *CDC2L2*) and *CDK11B* (*CDC2L1*), are serine/threonine kinases belonging to the cyclin-dependent kinase (CDK) family. These isoforms arise from alternative splicing of a common precursor mRNA and share ~97% amino acid sequence identity, differing primarily in their C-terminal regions. Both proteins interact with cyclin L to form active kinase complexes involved in regulating RNA transcription, splicing, and cell cycle progression, particularly during the G2/M phase. CDK11B, the more extensively studied isoform, plays critical roles in spindle assembly, sister chromatid cohesion, and apoptosis. Antibodies targeting CDK11A/B are essential tools for investigating their distinct and overlapping functions. They are widely used in techniques like Western blotting, immunofluorescence, and immunoprecipitation to study localization, protein interactions, and expression patterns in normal and diseased states. Due to their high sequence homology, antibody specificity validation is crucial to avoid cross-reactivity. Dysregulation of CDK11 signaling has been implicated in cancers, neurological disorders, and viral infections, making these antibodies valuable for both basic research and therapeutic target validation. Recent studies also highlight their potential role in modulating transcription elongation through phosphorylation of RNA polymerase II.