The study explores the relationships between decision-making styles in hospital nurses and their attachment styles in adulthood as well as the possible mediation of these associations by self-regulation. It is based on the assumption that attachment styles, defined as mental working models of self and others, affect the decision-making process in nurses, whose profession includes frequent interaction with other people. The research sample included 161 nurses from the Children’s University Hospital in Bratislava, Slovakia. Attachment styles were measured by the Relationship Questionnaire, self-regulation by the Self-regulation Scale, and decision-making styles by the Melbourne Decision Making Questionnaire. Correlation analysis showed that two insecure attachment styles (anxious-preoccupied and fearful-avoidant) correlated positively with the preference of maladaptive decision-making styles (hypervigilance, buck-passing and procrastination). Mediation analysis revealed that these relationships are mediated by self-regulation, which means that the effect of attachment styles on decision-making styles might be carried by self-regulation ability. The results point to the role that attachment might play in the specific context of nursing.