Tumor-associated macrophages (TAMs) influence tumor progression and immune checkpoint blockade (ICB) efficacy. Interferon (IFN)-TAMs predict better survival and ICB responses, yet the mechanisms governing IFN-TAMs remain unclear. Here, we identify NDUFA4, a complex IV subunit of the electron transport chain, as a functional switch controlling TAM function and anti-tumor immunity. NDUFA4 expression sustained pro-tumoral TAMs. However, intratumoral IFNs decreased NDUFA4 expression in TAMs via the cooperative action of NDUFA4L3 and miR-147, co-encoded by a conserved bifunctional transcript. Mechanistically, NDUFA4 repression increased mitochondrial DNA release into the cytoplasm and subsequent STING activation, thereby amplifying anti-tumor IFN-induced transcriptional programs in TAMs. Finally, we designed RNA-based therapeutics that leveraged the specificity of miR-147 for the Ndufa4 transcript to enhance ICB efficacy and inhibit B16 melanoma tumor growth. These findings uncover mitochondrial complex IV remodeling as a critical mechanism governing the functional adaptation of macrophages to distinct microenvironments with broad implications for immunotherapy.