The purpose of this work is to analyze the impact of the expansion of the Brazilian winter corn crop on spot price seasonality in different regions of the country. We used the Bai & Perron (2003) procedure to identify structural breaks endogenously, considering spot prices for different regions (Cascavel-PR, ChapecóSC, Mogiana-SP, Rio Verde-GO, and Triângulo Mineiro-MG). Within each regime identified, harmonic parameters were obtained using the Ordinary Least Squares (MQO) method. Results showed that, with the growth of the winter corn crop in Brazil, the price fluctuation started to depend to a lesser extent on its seasonal pattern, except for Rio Verde-GO. In addition, we found evidence that price seasonality changed in 2010s, with lower prices during the harvest of the winter crop (May to August) and higher prices during the planted period (January to March). These findings should offer insights for marketing and risk management strategies and contribute to the design and execution of policies that aim to reduce the variations in the income of producers.