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Adenosine accumulation within the tumour microenvironment is a major barrier to effective cancer immunotherapy, driving potent immunosuppression through adenosine receptor signalling. While current clinical strategies primarily target the A_2A adenosine receptor, emerging evidence suggests that adenosine-mediated immune regulation, particularly in human myeloid cells such as macrophages, involves coordinated signalling through both A_2A and A_2B receptors. In this study, we define for the first time the adenosine receptor pathways responsible for the immunosuppressive effects of the adenosine analogue 5'-N-Ethylcarboxamidoadenosine (NECA) in human monocyte-derived macrophages and determine the downstream consequences for T cell function. NECA-conditioned macrophages acquired an immunosuppressive, M2-like phenotype, characterised by reduced production of pro-inflammatory cytokines (IL-12, IL-23, IL-6, TNFα) and increased expression of VEGF-A and IL-10. Functionally, these macrophages impaired T cell effector responses, markedly reducing Th1-type responses as indicated by ablation of IFNγ production. Importantly, reversal of macrophage polarisation and restoration of T cell function could be achieved by simultaneous blockade of both A_2A and A_2B receptors. These findings identify the potential of simultaneously inhibiting the A_2A and A_2B receptors as a novel key strategy for overcoming adenosine-driven immunosuppression and enhancing the efficacy of cancer immunotherapies targeting the tumour microenvironment.