Tumor metabolism is one of the recognized hallmarks of cancer. Investigations into the distinct metabolism of tumor cells compared to normal untransformed cells were initiated almost a century ago by Otto Warburg. Technical advances, especially in chromatography, mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy, and imaging techniques such as positron emission tomography (PET), have improved our understanding of the metabolic changes in tumors, including in pheochromocytomas and paragangliomas (PPGLs). PPGLs due to mutations in Krebs cycle genes, including succinate dehydrogenase (SDH) subunits, fumarate hydratase (FH), and malate dehydrogenase 2 (MDH2), in particular illustrate how metabolism is linked to downstream cellular signaling pathways involved in tumorigenesis. Such changes in metabolism can provide useful biomarkers for diagnosis and disease stratification. Changes in metabolism can also impact stromal cells of the tumor microenvironment, which can contribute to energy requirements of mutated tumor cells. Elucidation of the underlying changes in metabolism is further enabling identification of potential metabolic targets for therapeutic intervention.