Since heavy metals and trace elements have negative effects on the oxidative stability of olive oil and human health, the aim of this study was to determine the concentrations of iron, the element important for the assessment of olive oil quality. The analysis of this trace element, in 35 samples of olive oil, originating from the Republic of Croatia, were performed by atomic absorption spectrometry using graphite technique. The samples of olive oil contain a high proportion of lipid components, and thus represent a complex organic system for the determination of metal. In order to obtain a homogeneous solution suitable for the determination of metal by graphite technique, all analyzed samples were previously prepared using a microwave digestion system. The obtained results have shown the advantages of iron concentration determination by graphite technique after removal of complex matrix by burning samples by microwave-assisted digestion. Low RSD values point out the exceptional/satisfactory repeatability of microwave digestion procedures and the metal concentration determination by graphite technique. Based on the obtained LOD and LOQ values as well as the defined NDK, conducted graphite technique methods can be considered as suitable to determine the analyzed metal in olive oils. The concentrations of iron in the investigated olive oils were below their maximum permissible concentrations as defined by the valid rulebook, except in one sample. The presented data point to the exceptional quality of Croatian olive oils. Further research should be conducted to evaluate the presence of other metals in the investigated olive oil samples. The investigated olive oils are categorized as extra virgin olive oil, while a small number of samples are classified into the group of virgin olive oil.