Studying metabolism in the different cellular compartments of the tumor microenvironment (TME) is crucial to identify the specific metabolic signatures that contribute to tumor progression. Additionally, TME-driven metabolic changes can disrupt the essential metabolic processes involved in immune cell function, hindering immunotherapy success. Extracellular flux analysis (Seahorse) is a well-established approach used to characterize cellular metabolism. When combined with flow cytometry-based measurements, it offers a comprehensive view of the metabolic signatures within the different cellular compartments of the TME. Here we provide a detailed description on the procedures of Seahorse analysis and complementary flow cytometry-based metabolic readouts on tumor cells and T cells in the context of cancer, which can also be applied to other physiological and pathological situations.