Upon metastatic seeding in the liver, liver macrophages, including Kupffer cells, acquire a transcriptional profile typical of tumor-associated macrophages (TAMs), which support tumor progression. MicroRNAs (miRNAs) fine-tune TAM pro-tumoral functions, making their modulation a promising strategy for macrophage reprogramming into an anti-tumoral phenotype. Here, we analyze the transcriptomic profiles of liver and splenic macrophages, identifying miR-342-3p as a key regulator of liver macrophage function. miR-342-3p is highly active in healthy liver macrophages but significantly downregulated in colorectal cancer liver metastases (CRLMs). Lentiviral vector-engineered liver macrophages enforcing miR-342-3p expression acquire a pro-inflammatory phenotype and reduce CRLM growth. We identify Slc7a11, a cysteine-glutamate antiporter linked to pro-tumoral activity, as a direct miR-342-3p target, which may be at least partially responsible for TAM phenotypic reprogramming. Our findings highlight the potential of in vivo miRNA modulation as a therapeutic strategy for TAM reprogramming, offering an approach to enhance cancer immunotherapy.