The dividend distribution policy defined by managers is an important decision for corporate growth and for transmitting information to investors about the future of the business. This article analyzes the impact of dividend distribution announcements on the stock prices of companies listed on the Iberian indices (IBEX35 and PSI) between 2022 and 2023, using the event study methodology. 19 Portuguese and 21 Spanish companies were analyzed. The results show that investors in both markets anticipated dividends below expectations, given the formation of negative abnormal returns even before the distribution was announced. A few days after the announcement, the oscillation of average abnormal returns contracted, suggesting the advantages of diversifying investments in the Iberian markets. However, the significance of the effects does not disappear, suggesting evidence against the semi-strong form of market efficiency. It is therefore important to raise awareness among managers, investors and regulators of the usefulness of resources to support strategic financial decision-making based on digitalization and big data, and to strengthen financial literacy in society.