Studies have shown that silver nanoparticles (AgNPs) and zinc oxide nanoparticles (ZnONPs) can cause adverse effects on aquatic organisms. When nanoparticles (NPs) present together in aquatic environments, they can interact with each other through physical and chemical processes. The purpose of this study was to investigate the effect of the presence of ZnONPs on the toxicity of AgNPs using Artemia as a model saltwater aquatic organism. This study was conducted using ISO /TS 20787 standard method. Instar I and II of Artemia salina nauplii were exposed to different concentrations of AgNPs in the presence of 0, 1, 10, and 100 mg/L ZnONPs and the immobilization were assessed during 48 hours (35 g/L water salinity, 28 °C temperature and complete darkness). Data were analyzed using the EPA Probit program. The 48h EC50s of AgNPs in the presence of 0, 1, 10, 100 mg/L ZnONPs were 26.20, 25.41, 24.20, 22.61 mg/L for Instar I and 24.98, 24.20, 21.74, 16.06 for Instar II, respectively. Accordingly, instar II was more sensitive than instar I. Also, the toxicity of AgNPs increased in the presence of ZnONPs. This study showed that the combination of AgNPs and ZnONPs can result in a synergistic effect on the toxicity to Artemia nauplii. Further research is needed to understand the mechanisms underlying these interactions and their implications for environmental risk assessment of these nanoparticles.