In this investigation, duplex steel 1.4462 was subjected to the microstructural analysis and Vickers hardness measurements. The tests were performed on three characteristic surfaces, considering the rolling direction. Obtained results showed that this duplex steel exhibits an increase in measured hardness with the increase of the applied load, known as the reverse indentation size effect (RISE). The following mathematical models were used for the phenomenon explanation: Meyer’s law, proportional specimen resistance (PSR) model and modified proportional specimen resistance (MPSR) model. The regression analysis showed that all models can be used for the RISE analysis in duplex steel. "True" Vickers hardness was determined by the PSR and MPSR models. The MPSR model was more suitable in this particular case, because it considers the effect of the finishing process on the hardness results and gives the "true" hardness closest to the measured value.