Previous whole-exome sequencing has demonstrated that melanoma tumours harbour mutations in the GRIN2A gene. GRIN2A encodes the regulatory GluN2A subunit of the glutamate-gated N-methyl-D-aspartate receptor (NMDAR), involvement of which in melanoma remains undefined. Here, we sequenced coding exons of GRIN2A in 19 low-passage melanoma cell lines derived from patients with metastatic melanoma. Potential mutation impact was evaluated in silico, including within the GluN2A crystal structure, and clinical correlations were sought. We found that of 19 metastatic melanoma tumours, four (21%) carried five missense mutations in the evolutionarily conserved domains of GRIN2A; two were previously reported. Melanoma cells that carried these mutations were treatment-naïve. SIFT analysis predicted that S349F, G762E and P1132L would disrupt protein function. When modelled into the crystal structure of GluN2A, G762E was seen to potentially alter GluN1-GluN2A interactions and ligand binding, implying disruption to NMDAR functionality. Patients whose tumours carried nonsynonymous GRIN2A mutations had faster disease progression and shorter overall survival (P < 0.05). This was in contrast to the BRAF V600E mutation, found in 58% of tumours but showing no correlation with clinical outcome (P = 0.963). Although numbers of patients in this study are small, and firm conclusions about the association between GRIN2A mutations and poor clinical outcome cannot be drawn, our results highlight the high prevalence of GRIN2A mutations in metastatic melanoma and suggest for the first time that mutated NMDARs impact melanoma progression.