Introduction: The pressure ulcer is a persistent public health problem, with burden to patients, family and health institutions. Health professionals should have appropriate knowledge to ensure the effectiveness on preventing of these injuries and treat them properly when they happen. Objectives: Describing the knowledge of nursing professionals about prevention of pressure ulcers and analyzing their opinion on the same. Methodology: It is characterized as an exploratory, descriptive and quantitative study conducted from January to June 2015, in a University Hospital; approved by the Ethics Committee of the institution. For data collection it was used the Pieper knowledge test and questions about opinions of professionals referring to the thematic. Results: The study subjects were 32 nurses and 37 assistants/nursing technicians. The results showed approximate averages of correct answers in the general context of the knowledge test among nurses (75.60%) and assistants/nursing technicians (76.29%). It was found out that those professionals recognize the importance of preventing the injury, assure to be performed in the units where they work, but mention difficulties. Conclusion: There were identified knowledge gaps about the pressure ulcer and its prevention, in both professional categories, which should be considered when planning strategies for staff training.