The substitution R1032Q is the most frequent non-synonymous mutation of the vascular endothelial growth factor receptor 2 (VEGFR2) in cancer patients, classified as a loss-of-function variant. Here we characterize the molecular bases of its role in cancer, demonstrating that it lacks significant activity and pro-oncogenic effects in VEGFR2-negative tumor cells, while being able to sustain the tumorigenic potential of VEGFR2-positive cancer cells. By implementing a cell model that allows expression of either VEGFR2(R1032Q) alone or in combination with VEGFR2(WT), we showed that the effects of mutated VEGFR2 are at least in part due to the ability of VEGFR2(R1032Q) to form functional heterodimers with co-expressed VEGFR2(WT) that result in increased kinase activity and receptor phosphorylation. This was associated with reduced mobility of the receptor on the membrane, linked to its translocation into detergent-resistant membrane (DRM) domains (e.g. lipid rafts), which showed alterations in lipid compositions and structure. These data shed light on a novel oncogenic mechanism of activation of VEGFR2, clarifying the paradoxical loss-of-function nature of the substitution R1032Q of VEGFR2.