In this work, a boron-doped diamond (BDD) electrode was used for the electroanalytical determination of indole-3-acetic acid (IAA) phytohormone by square-wave voltammetry. IAA yielded a well-defined voltammetric response at + 0.93 V (vs. Ag/AgCl) in Britton-Robinson buffer, pH 2.0. The process could be used to determine IAA in the concentration range of 5.0 to 50.0 mM (n = 8, r = 0.997), with a detection limit of 1.22 mM. The relative standard deviation of ten measurements was 2.09 % for 20.0 mM IAA. As an example, the practical applicability of BDD electrode was tested with the measurement of IAA in some plant seeds.