A simultaneous second order derivative spectrophotometric method was developed for the determination of indium (III) and iron (II) using 2-hydroxy-3-methoxy benzaldehyde thiosemicarbazone (HMBATSC) as a chromophoric reagent. The reagent reacts with indium (III) and iron (II) at pH 6.0. In (III) and Fe (II) present in the mixture were simultaneously determined without solving the simultaneous equations by measuring the second order derivative amplitudes at 428 nm and 407 nm respectively. The derivative amplitudes obey Beer’s law in the range 0.131-4.592 μgml-1 of In (III) and 0.109-3.965 μgml-1 of Fe (II). Large number of foreign ions does not interfere in the present method. The present simultaneous method was used for the determination of micro amounts of indium (III) and iron (II) in synthetic mixtures.