Mantle cell lymphoma (MCL) is a heterogeneous B-cell non-Hodgkin lymphoma with typically high 18F-fluorodeoxyglucose (18F-FDG) avidity. The role of 18F-FDG positron emission tomography/computed tomography (PET/CT) has expanded significantly, encompassing disease staging, treatment response assessment, and prognostication. For staging, 18F-FDG PET/CT improves detection of nodal and splenic disease and frequently alters management, though bone marrow biopsy and gastrointestinal endoscopy remain necessary due to limited sensitivity. During treatment response evaluation, end-of-treatment 18F-FDG PET/CT assessed by Lugano/Deauville criteria consistently predicts progression-free survival. 18F-FDG PET/CT negativity before autologous stem cell transplantation is associated with improved outcomes. Regarding prognostication, baseline metabolic tumor volume and radiomic heterogeneity indices independently predict outcome, offering additional risk stratification beyond clinical or biological scores. Future directions include integration of PET-derived radiomic biomarkers with molecular MRD assays to achieve precision response-adapted management.