Uncertainty affects all markets, including the cereals market. During the 21st century, it is possible to highlight the impact of three major conditions of insecurity, i.e. the global financial crisis from 2009, which led to a recession in the Republic of Croatia that lasted for 6 years, the impact of the COVID-19 pandemic, and the war in Ukraine. Special emphasis was placed on this third condition of insecurity due to the fact that Russia and Ukraine are the countries that are considered the largest grain producers, and at the same time there is an embargo on the import of goods from Russia, while at one time it was impossible to export grain from Ukraine due to the war itself. For the purposes of this work, the influence of three selected conditions of uncertainty on the movement of grain prices was analyzed, that is, wheat and barley as the two types of grain for which there is the highest level of demand. These are cereals that are a production input in numerous production processes, therefore, changes in the price of these cereals are reflected in the price movements of a large number of other products. When it comes to produced quantities, they cannot vary significantly in the short term due to the specifics of the production process. In other words, there may be a significant decrease in the produced quantities due to the effects of bad weather, while it is almost impossible to significantly increase the produced quantities in a short period of time. It is possible to point out that the global financial crisis led to a drop in grain prices, which lasted throughout 2009. On the other hand, the other two conditions of uncertainty led to the appearance of a very short-term drop in grain prices, which was followed by a strong price increase, based on which it can be concluded that the COVID-19 pandemic and the war in Ukraine influenced the growth of grain prices.