The family, as one of the oldest communities of society, has undergone many changes in its structure throughout history. In Croatia, over the last few decades, there has been a trend of a decrease in the percentage of married couples with children in the overall demographic picture, and an increase in the number of single-parent families. Single-parent families are created in three ways: the death of one parent, the birth of a child out of wedlock, and divorce. The aim of this study was to examine differences in the experience of parenting stress, and self-assessments of maternal parenting competence in single-parent families concerning the number of children, and the type of single-parent family in which they live. The study involved 150 female respondents (mean age = 38 years, 50 widows, 50 divorced mothers, and 50 unmarried mothers) who completed a paper-pen questionnaire. The questionnaire consisted of the Parental Stress Scale, the Parental Competence Self-Assessment Scale, and the General Data Questionnaire. The results show that mothers differ in perceived levels of stress, but not in self-assessment of parental competence concerning the number of children they care for. Mothers with one child experience higher levels of parenting stress than mothers who care for two or more children. Mothers do not differ in the perceived level of stress or self-esteem of parental competence concerning which type of single-parent family they belong to, or whether they are widowed, divorced or unmarried. A moderate negative correlation was found between the perception of one's effectiveness in the parental role and the experience of parental stress, ie greater self-perception of parental effectiveness was associated with lower levels of perceived parental stress. A moderate negative association was found between satisfaction with fulfilling the parental role and experiencing parental stress, ie greater satisfaction with fulfilling the parental role was associated with lower levels of experiencing parental stress.