• The pro-photosensitizer predominantly keeps photodynamically inactive in the vasculature at pH 7.4. • The pro-photosensitizer transforms into a conjugated BODIPY photosensitizer by tumor-associated acidic extracellular matrix (pH 6.5–6.8) and lysosomes (pH 4.5-5.5). • Pro-photosensitizer with tumor-targeting moieties allows the prodrug to target tumor tissues. • A reversible interconversion between photosensitizer and pro-photosensitizer. Recent advances in photodynamic therapy (PDT) require the selective sensitization of the targeted disease to avoid undesired side effects. The development of photosensitizers that are photodynamically silent until reaching their respective target is one of the most promising strategies to avoid background accumulation in non-target tissue. Here, we report a colorless/nonconjugated leuco-BODIPY pro-1 covalently linked to targeting tumor-associated polyamine substituent. Pro-1 predominantly keeps photodynamically inactive in the vasculature at pH 7.4. After targeting the elevated polyamine transporters in neoplastic cells, pro-1 transforms into a conjugated BODIPY photosensitizer 1 by tumor-associated acidic extracellular matrix (pH 6.5–6.8) and the neoplastic increased abundance of lysosomes (pH 4.5–5.5). The phototoxicity of 1 effectively inhibits the growth of tumors (86% by volume) on tumor-bearing mice. More importantly, during the PDT treatment, photosensitizer 1 remains the leuco-BODIPY form in the vascular system and the extracellular matrix of normal tissues, reducing the side effect of long-lasting photosensitivity.