Anxiety can be described as an unpleasant and disturbing subjective experience that prepares the body to respond to a potential threatening situation. It is often associated with several cognitive processes, among which is the cognitive style characterized by rumination. Rumination is characterized by preoccupation with repetitive thoughts that arise from focusing on one's own symptoms of distress. Due to the negative affect that both anxiety and rumination lead to, both mentioned constructs can cause cognitive and functional changes in such a way that they interfere with the daily processes necessary for the normal functioning of the individual. Among these processes is sleep, which plays an important role in health and in increasing the quality of life. Disturbed sleep quality can have numerous negative outcomes for an individual's mental and physical health, and therefore it is important to know the processes that can disturb it. For this reason, the aim of this research was to examine the relationship between anxiety, rumination and sleep quality. The sample consisted of 171 students of the University of Zadar, of which 68 were male and 103 were female, with an average age of 21. Data were collected live using the paper-pencil method, and the Anxiety Scale from the Depression, Anxiety and Stress Scale (DASS) was used to measure anxiety, the Ruminative Thinking Style Scale (RTS) was used for rumination, and the Pittsburgh Sleep Quality Index (PSQI) was used for sleep quality. The general data questionnaire consisted of questions about the average success of the study that the participants achieved in the previous semester, and about their age. The remaining data about the study, study year and gender were recorded by the researcher. In accordance with expectations, it was shown that more anxious individuals ruminate more and have worse sleep quality.