Cancer is characterized by uncontrolled proliferation of cells and remains a major health burden across the globe. Altered metabolism/abnormal metabolic signaling are the key features of cancer progression. Conventional therapy for cancer possesses various limitations, such as drug resistance, low targeting ability, limited tissue distribution, off-targeted effects, high doses, and systemic toxicity. Current advancements have harnessed the exclusive properties of nanomaterials for diagnosis and treatment of cancer via targeted drug delivery, improved imaging, and precise therapeutic action with negligible toxicity. Nanotheranostics integrate bioimaging and therapeutic functionalities. Exploring cancer metabolic abnormalities via nanotheranostics provides a novel strategy for early diagnosis, real-time monitoring, and therapy for cancer progression. This book chapter highlights various theranostic nanoformulations designed to modulate cancer cell metabolism such as glucose metabolism, lactate metabolism, amino acid metabolism, nucleotide metabolism and lipid metabolism. These nanotheranostics exploits tumor-specific metabolic vulnerabilities, offering promising strategy to enhance diagnostic accuracy and therapeutic efficacy in cancer treatment.