This study investigated the potential of quercetin, a flavonoid with anticancer properties, to enhance the effectiveness of the chemotherapy drug doxorubicin in primary and metastatic uveal melanoma cells. The results showed that the combination of quercetin and doxorubicin significantly increased doxorubicin accumulation in cancer cells and decreased cell viability, suggesting that quercetin may act as a chemosensitizer for doxorubicin. However, quercetin pretreatment did not increase the efficacy of the combination therapy. The study also identified a protein that plays a role in drug efflux that could be inhibited by quercetin to increase doxorubicin accumulation. Further investigation of the potential of quercetin in vivo is warranted.