<p>Cancer immunotherapy has revolutionized the treatment of certain malignancies by harnessing the power of the patient’s immune system to target cancer cells precisely. Despite significant advancements, the efficacy of immunotherapy is frequently hindered by intrinsic and extrinsic resistance mechanisms within the tumour microenvironment (TME). This review explains the complementary effect of using immunotherapies alongside other treatments and the need to identify the putative biomarkers to predict therapeutic activity and monitor the response to treatment. Biomarkers demonstrate considerable prospects in addressing the challenges of immunotherapy resistance by revealing tumour metabolic heterogeneity and dependence on other pathways. Moreover, the enhanced knowledge of extracellular vesicles and their effects on the TME might open up new insights, which would allow enhancing the effect of immunotherapy. In addition to this, several types of cancer immunotherapies, such as checkpoint inhibitors, cytokines, and CAR T-cell therapies, have shown excellent results in certain tumours, with inconsistencies in response rates and immune-related issues highlighting the importance of ongoing research. The given review article underlines the significance of biomarkers in diagnosing, prognosing, and monitoring diseases and suggests their integration into clinical practice to support the improved outcomes of patients and help to develop more efficient cancer drugs.</p>