In many countries, the word sustainability is used at the governmental and commercial level with a positive meaning about environmental care and social and animal welfare. The objective of this study was to evaluate the degree of knowledge that dairy producers have about sustainability and its association with milk production practices. The study was performed in the Southern region of Chile. Twenty-six farmers were surveyed by phone or email. The farms were selected through associations of milk producers and their willingness to participate. The questionnaire consisted of 39 questions, of which only one was an open-ended question. The survey considered general information on the characterization of the producer and his farm. Surveys were subjected to an exploratory descriptive analysis. Statistical tests on the data were performed by 2-dimensional contingency tables and using the Chi-squared test. The average age of the producers was 52 years old. Concerning the educational level, 48% of the producers have university studies and 52% technical studies. In 68% of the cases, those studies were related to the agricultural area. 92% of the producers grew in the field. 41.6% of the farms have less than 200 cows. The average area was of 276 ha, with a stocking rate of 1.3 cows·ha⁻¹. All producers declared to have heard the word sustainability; however, 12% said that they did not know a definition. Among the definitions of sustainability that cover most of the concepts mentioned are “resource use in an efficient way that ensures profitability and does not compromise resources in the future” and “that cycles can be replicated without harming the environment.” About knowledge of the management associated with sustainable production there was no relationship between the level of knowledge and education; besides, of 19 sustainable practices mentioned, about 90% of the answers were correct. 84% of producers indicated that the focus of their exploitation was production and 79% gave greater importance to profitability than to the animal welfare. This study can be helpful for public policymakers due to the need to improve strategies to transfer knowledge of sustainable practices. This need is reflected in the lack of implementing sustainability through a set of practices.