(1) The COVID-19 pandemic is a global epidemic crisis situation with negative health consequences. This study aimed to determine the mediatory role of self-efficacy in correlations between dispositional optimism and loneliness (both general loneliness and social and emotional loneliness) among Polish nursing students during the COVID-19 pandemic. (2) The study involved 894 students from six Polish universities. A diagnostic survey was used as the research method, and the Scale for the Measurement of Loneliness Scale (DJGLS), Life Orientation Test (LOT-R), and the Generalized Self-Efficacy Scale (GSES) were used to collect data. (3) The mean subject age was 20.73 years (SD = 1.81). More than half (51.01%) of the respondents scored high on the GSES scale, indicating an individual's belief in the self-efficacy in coping with difficult situations and obstacles. However, 40.60% scored low on the LOT-R scale, indicating that the respondents were pessimistic. The mediation analysis revealed that self-efficacy plays a partial mediatory role in correlations between dispositional optimism and loneliness in general, social and emotional loneliness. (4) It is important to undertake loneliness prophylactic and prevention activities among nursing students and to develop personal resources, i.e., optimism and self-efficacy, to effectively offset the effects of the COVID-19 pandemic.
Keywords: COVID-19; loneliness; optimism; pandemic; self-efficacy; student.