The aim: Exploring the specifics of the underlying mental states of university students in the context of online learning during the COVID-19 pandemic and identifying their relationship to mental health. Materials and methods: The study of mental states was carried out using three valid methods, namely: a clinical questionnaire for the detection and evaluation of neurotic states (K. Yakhin, D. Mendelevich), a questionnaire for diagnosing the level of social frustration (L. Wasserman, adaptation of V. Bojko), State-Trait Anxiety Inventory (STAI) (Ch. Spielberger, adaptation by Yu. Khanin). The author’s questionnaire (L. Borysenko) was used to study the connection between the factors of online learning and emotional states of students. The obtained empirical data were subjected to qualitative and quantitative processing. Results: The analysis of the obtained data allows to state the fact of predominance of high and increased level of situational and personal anxiety in the subjects in the conditions of online learning. In the process of psychodiagnosis of neurotic states, it was found that most students have a level of painful or borderline mental conditions such as anxiety, neurotic depression, asthenia and autonomic disorders. It was found that students have an elevated level and high level of social frustration. The main factors of online learning, which, according to students, cause them to deteriorate mental health are: forced to stay in a confined space, lack of direct social contacts, prolonged stay in a static position, increased study load and volume of tasks, anxiety for academic success and quality professional training, concern for their health and the health of their loved ones. Conclusions: The forced transition to online learning due to the COVID-19 pandemic has negatively affected the mental state of many students. In most respondents, this manifested itself in increased anxiety, depression, autonomic reactions due to limited opportunities to communicate with teachers and classmates, new learning conditions and increased workload.