The use of trace elements such as indium and gallium has increased rapidly due to the extensive application of electronic devices. These technology-critical elements (TCEs) can be potentially released into the aquatic environment during semiconductor manufacturing or disposal of E-wastes. However, there is a lack of information about the bioavailability and toxicities of indium and gallium to higher tropic levels of aquatic organisms such as fish. In this context, we aim to understand the toxic effect of indium and gallium ion species, and their modes of toxic actions are investigated by employing embryo-larval and juvenile medaka (Oryzias latipes) as a model organism. The fish embryo’s malformation and survival, hatching, heart-beating rate were observed and measured within 6 days of exposure. The locomotor activities of larval fish were analyzed after 3 days-post-hatching. The acute toxicity and bioconcentration of juvenile fish were analyzed after 7 days of exposure. The results indicated that both indium and gallium were only mildly toxic with the 7-day LC50 of juvenile medaka being 198 (155-245) mg/L and 89 (71-112) mg/L, respectively. Only gallium showed significant embryo mortality at concentrations of 100-500ppm, with a LC50 of 351 (290-424) mg/L. Both elements showed delayed hatch time and decreased rates of hatching and heart-beat at the same ranging. Overall, this study provided a perspective on the evidence of indium and gallium toxic effects among the early life cycle of medaka fish. The subsequent research will further investigate the modes of toxic actions of indium and gallium in terms of developmental toxicity in early life stages of medaka.