The electrochemical behavior of arsenic(III) and indium(III) is investigated in the ethaline deep eutectic solvent (a mixture of 1 mol eq. of choline chloride and 2 mol eq. of ethylene glycol) using As2O3 and InCl3 as precursors. Cyclic voltammetry of ethaline solutions containing individual As(III) and In(III) reveals that the thermodynamic deposition potential of As is more negative than that of In in ethaline, in contrast to what has been observed in aqueous solutions. When In(III) is mixed with As(III), the reduction of In(III) shifts positively while the reduction of As(III) shifts negatively with respect to that of individual solutions. Co-deposition of In-As is attempted using potentiostatic electrolysis on Cu and Ni substrates, respectively. The electrodeposited films are characterized with scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and X-ray powder diffraction (XRD). The As/In atom ratio in the obtained deposits increases as the deposition potential gets more negative. Crystalline InAs film can be obtained from the ethaline solution contains a As(III) concentration higher than that of In(III). However, the co-deposits turn into amorphous once the As content in the deposits exceeds that of In. (c) 2019 The Electrochemical Society.