The submitted paper aims at CSR activities and marketing communication of food companies in Slovakia and its influence on consumer behaviour and their decision-making. On the threshold of the 3rd millennium, the CSR of food companies is also connected with rationality and irrationality in creating preferences in consumer shopping behaviour. Corporate social responsibility (CSR) has received much attention in recent years. Food companies are currently using CSR to gain a competitive advantage, and these activities have also penetrated the marketing field. In the field of CSR and the food market in the Slovak Republic, we conducted a survey based on a questionnaire focused on CSR activities as a marketing tool in the food market from the customers’ perspective. In the questionnaire, the most important problems and aspects related to the CSR issue were examined and transferred to the questionnaire offered to online respondents. We ensured the representativeness of the research sample by addressing the questionnaire to target interest groups and respondents of all age categories focused on the food market. Three research questions were set for analysing corporate social responsibility as a marketing tool of food companies in Slovakia from the consumer’s point of view. The questionnaire survey results with 1,254 participating respondents showed that although they are familiar with the concept of CSR, a large percentage of respondents need to learn about these activities or pay more attention to them. Based on our conducted research, customers perceive the CSR activities of food companies in most cases as a marketing communication tool that builds the company’s good name and image. We can also observe a huge impact in the area of rationality and irrationality when creating preferences in the purchasing behaviour of consumers based on CSR activities and their implications and communications with customers. We used the Chi-square test, proportional Z test, two-sample and frequency and contingency tables to evaluate the data statistically. Communication of CSR activities is a difficult task for food companies, which currently brings many threats and opportunities. For this reason, businesses need the right CSR communication strategy to influence consumer attitudes and behaviour effectively. CSR in the food industry is particularly important because of the wide range of potential benefits.