Immune monitoring of cell therapies is a complex and evolving topic, particularly in the rapid expanding field of chimeric antigen receptor T (CAR-T) cell applications. Defining essential, recommended, and optional immune monitoring data post-CAR-T cell infusion is crucial to improve patient outcomes and inform post-treatment decisions. To address this gap, we conducted a survey-based study across centers affiliated with the European Society for Blood and Marrow Transplantation (EBMT), focusing on patients treated with European Medicines Agency (EMA)-approved CAR-T products. Building on a thorough review of the literature, we mapped the current landscape of immune monitoring practices and assessed their impact on clinical management. By defining the state of the art in the field, this work marks an initial step towards a structured harmonization process potentially able to enhance the management and outcomes of patients undergoing these immune cell therapies.