This article aimed to verify whether social marketing communications are effective to bring changes in attitudes in a group of individuals, regarding the consumption of organic food. As a secondary objective, we intend to verify that the level of information available to individuals, it is a differential to encourage attitudes. Therefore, it was used an experimental methodology, and as techniques of comparative analyses, the non-parametric test for independent samples "Jonckheere-Terpstra" and "Mann-Whitney". The experiment was conducted with three different groups, a control group that received no manipulation and two experimental groups that were exposed to different levels of marketing communications. The control group, which received no communication, had less favorable attitudes than the experimental groups to the consumption of organic food, which allowed inferences about the influence of social marketing in changing attitudes of individuals. Among the most important findings, we found that receiving much information does not necessarily result in a positive effect, because the experimental group that received less information than the other one, showed more favourable attitudes.