Zika virus (ZIKV) is an emerging mosquito-borne virus of medical concern. ZIKV infection may represent a serious disease, causing neonatal microcephaly and neurological disorders. Nowadays, there is no approved antiviral against ZIKV. Several indigenous or endemic medicinal plants from Mascarene archipelago in Indian Ocean have been found able to inhibit ZIKV infection. The purpose of our study was to determine whether essential oil (EO) from Reunion Island medicinal plant Ayapana triplinervis, whose thymohydroquinone dimethyl ether (THQ) is the main component has the potential to prevent ZIKV infection in human cells. Virological assays were performed on human epithelial A549 cells infected with either GFP reporter ZIKV or epidemic viral strain. Zebrafish assay was employed to evaluate the acute toxicity of THQ in vivo. We showed that both EO and THQ inhibit ZIKV infection in human cells with IC 50 values of 38 and 45 µg/mL, respectively. At the noncytotoxic concentrations, EO and THQ reduced virus progeny production by 3-log. Time-of-drug-addition assays revealed that THQ could act as viral entry inhibitor. At the antiviral effective concentration, THQ injection in zebrafish does not lead to any signs of stress and does not impact fish survival, demonstrating the absence of acute toxicity for THQ. From our data, we propose that THQ is a new potent antiviral phytocompound against ZIKV, supporting the potential use of medicinal plants from Reunion Island as a source of natural and safe antiviral substances against medically important mosquito-borne viruses.