Th e fi nancial markets are impacted by various seasonal anomalies. One of the best known of them is the Halloween eff ect. Th e Halloween eff ect means that the summer period (May-October) asset returns are lower compared to the winter period (November-April) asset returns. In the paper, price series of 20 major agricultural commodities over the 1980-2015-time period are tested for the presence of the Halloween eff ect. Th e data show that 15 out of the 20 commodities recorded a higher average winter period than summer period returns and in 10 cases, the diff erences are statistically signifi cant. Th e data also show that out of the 5 commodities with higher summer period returns, only in the case of poultry the diff erences are statistically signifi cant.