Mitochondria play essential roles in cellular metabolism and signaling, regulating biosynthetic pathways, calcium homeostasis, redox balance, and cell fate beyond ATP production. Their continual remodeling through fusion, fission, and mitophagy maintains mitochondrial quality control and adapts organelle function to cellular demands. Here, we review how mitochondrial dynamics, fusion, fission, and mitophagy modulate metabolic reprogramming and signaling to drive cancer progression and therapy resistance. Emerging evidence indicates that in cancer, mitochondrial fusion enhances respiratory efficiency and oxidative phosphorylation, whereas fission promotes glycolytic adaptation, rapid biomass accumulation, and stress tolerance. Mitophagy further refines metabolic fitness by eliminating damaged mitochondria and sustaining redox homeostasis. Together, these processes underscore that dysregulation of mitochondrial dynamics is a hallmark of cancer and a key driver of metabolic reprogramming and therapeutic resistance. In this review, we summarize how mitochondrial fusion, fission, and mitophagy govern metabolic circuitry in cancer development and therapy resistance. We highlight their functional impact on tumor progression and discuss emerging therapeutic strategies targeting mitochondrial dynamics and associated machinery. Understanding this dynamic metabolic crosstalk may reveal new vulnerabilities and guide the development of mitochondria-targeted cancer therapies.