Mitochondrial function in white adipose tissue (WAT) is an important yet understudied aspect of adipocyte biology. Here, we report a role for amyloid precursor protein (APP) in compromising WAT mitochondrial function through a high-fat diet (HFD)-induced, unconventional mis-localization to mitochondria that further promotes obesity. In humans and mice, obese conditions induce substantial APP production in WAT and APP enrichment in mitochondria. Mechanistically, HFD-induced dysregulation of signal recognition particle subunit 54c is responsible for the mis-targeting of APP to adipocyte mitochondria. Mis-localized APP blocks the protein import machinery, leading to mitochondrial dysfunction in WAT. Mice overexpressing adipocyte-specific and mitochondria-targeted APP display increased body mass and reduced insulin sensitivity, along with dysfunctional WAT, owing to a dramatic hypertrophic program in adipocytes. Elimination of adipocyte APP rescues HFD-impaired mitochondrial function with considerable protection from weight gain and systemic metabolic deficiency. Our data highlight an important role for APP in modulating WAT mitochondrial function and obesity-associated metabolic dysfunction.