Single mothers are one of the most vulnerable populations during the coronavirus health crisis. The aim of this study was to determine the levels of perceived parenting stress, social support and psychological distress, as well as their associations, among single mothers during the coronavirus pandemic. The study included 67 single mothers of children under the age of 18. Levels of psychological distress, parenting stress and perceived social support, as well as sociodemographic data and data about the perceived changes of parenting stress and the availability of social support were collected using an online questionnaire. Results show that, on average, single mothers report high levels of psychological distress and moderate levels of parenting stress. On the psychological distress questionnaire, 41.79% of participants obtained results higher than the critical value, which indicates high prevalence of elevated psychological distress and the presence of psychopathological difficulties among single mothers during the pandemic. The level of perceived social support from family, friends and significant others was significantly lower compared to a representative sample of Croatians, but did not differ significantly from the level of social support of a comparabile group of single mothers surveyed before the pandemic. More than half of the participants reported increased level of parenting stress and decreased level of available social support in caring for their child during the pandemic, in comparison to the time prior to the pandemic. The results of this study can be applied in the assessment of needs for psychological interventions and preventive programs directed to the population of single mothers, as well as in the planning and implementation of such programs.