Companion diagnostics refer to the test or measurement which provides essential information about the patient’s genetic and genomic characteristics to the physicians for making treatment decision. This information is important for the safe and effective use of corresponding drugs and therapies in the treatment. Rise in awareness about personalized medicines, technological advancement and government initiatives are some of the major factors which are driving the companion diagnostics market. Companion diagnostics helps to improve clinical outcome and cost saving. Companion diagnostics are used in drug discovery and development in a cost effective manner. In addition, companion diagnostics also used to manage side effects from the drug and therapies. On the basis of technology, companion diagnostics market can be segmented into polymerase chain reaction (PCR), in-situ hybridization (ISH), immunohistochemistry (IHC) and others. On the basis of application, companion diagnostics market can be segmented into breast cancer, gastric cancer, lung cancer, colorectal cancer, melanoma and others. On the basis of end user, companion diagnostics market can be segmented into pharmaceutical companies, reference lab and others. Companion diagnostics methodology includes genetic tests platforms, enzyme-linked immunosorbent assays, immunohistochemistry, proteomic assays and others. Companion diagnostics reduce costs related to hospitalization due to unnecessary treatment.