Immunotherapy has shown great potential for treating aggressive cancers and it is becoming the fourth pillar of cancer therapy. However, tumors express molecules, such as the Programmed Death Ligand 1 (PD-L1), to prevent immune cells activity (immune-evasion). The immune checkpoint protein Programmed Death receptor 1 (PD-1) expressed by lymphocytes instructs T-cells not to attack any tumor cell expressing PD-L1. Several therapies anti PD-1/PD-L1 have been approved by FDA, but concerns have been raised about their efficacy and safety. Therefore, there is a need for different approaches to target this pathway. Copper transporter 1 (CTR1) and Copper levels are elevated in tumors and the use of copper targeting agents is currently under intense investigation. It has been also reported that copper plays a major role in the immune-system, but its activity is unclear. In this study we demonstrated that copper plays a key role in the expression of PD-L1 in cancer cells. Tissue microarrays from neuroblastoma (NB) and glioblastoma (GBM) patients showed a significant correlation between CTR1 and PD-L1 expression (p=0.00014 and p=0.012 respectively). In vitro experiments showed that downregulation of CTR1 caused a decrease of intracellular copper which in turn led to a downregulation of PD-L1 expression in cancer cells. On the other hand, addition of copper into the media clearly induced PD-L1 upregulation. Consistently, Dextran-Catechin (DC) and TEPA, drugs reducing copper, were able to downregulate PD-L1 expression in tumours. In vivo studies showed that copper lowering drugs prolonged mice survival, and ex vivo immunohistochemistry staining confirmed the downregulation of CTR1 and PD-L1 expression. In addition, 24h and 48h of DC treatments showed an increase of tumor-infiltrating CD4+ and CD8+ lymphocytes and activated NK cells in NB immune-competent mouse model. In conclusion, our results have shown that copper targeting drugs DC and TEPA are able to downregulate PD-L1 in vitro and in vivo by reducing intracellular copper levels, and this promoted a significant increase of tumor infiltrating lymphocytes.