In the last decade, immuno-oncology has revolutionized cancer therapy by harnessing the body's immune system to target and eliminate tumor cells, offering durable responses particularly in malignancies previously considered treatment-resistant. This approach exploits immune checkpoints, monoclonal antibodies, Chimeric Antigen Receptor (CAR) T-cells, and innovative cancer vaccines to activate, promote, and enhance immune responses specific to tumor-associated antigens. However, the complexity of tumor–immune interactions necessitates advanced tumor imaging techniques to accurately diagnose, monitor, and tailor effective immunotherapy techniques. Tumor imaging plays a pivotal role in visualizing immune cell infiltration, tracking immune responses in real-time, and identifying immune-related adverse events. Recent innovations such as hybrid Magnetic Resonance Imaging (MRI), Computed Tomography (CT), and Positron Emission Tomography (PET) (PET/CT and MRI) combined with novel tracers—like radiolabeled antibodies targeting Programmed Death-Ligand 1 PD-L1—allow precise quantification of immune activation within the tumor microenvironment. These modalities facilitate early assessment of therapeutic efficacy, guiding personalized treatment adjustments. Furthermore, multimodal imaging approaches integrating molecular and anatomical data improve the delineation of tumor boundaries, detect metastases, and evaluate emerging resistance mechanisms. As immuno-oncology moves toward personalized medicine, imaging biomarkers will be essential in stratifying patients most likely to benefit from immune-based therapies, predicting outcomes, and minimizing toxicity. Continued research in tumor imaging will enhance our understanding of immune dynamics, ultimately improving treatment precision and patient survival in cancer care. The main aim of this was to advance and develop the in-depth understanding and application of innovative tumor imaging techniques that accurately visualize and quantify immune responses within the tumor microenvironment. By enabling personalized immunotherapy strategies, improving personalized treatment and monitoring will significantly enhance patient therapeutic outcomes, as a result of appropriate treatment corresponding to effective and modern cancer care.