The present study was conducted to examine the mediating role of parent-child relationship in the association between responsibility and adjustment in single-parent adolescents in Tehran. This applied research had a descriptive-correlation design and it was based on structural equations. The statistical population of the study was comprised of single-parent teenagers aged 12-15 studying in the 7th, 8th and 9th grades of junior high school in Tehran. To determine the sample size based on Cochran's formula, 342 students were selected through convenience sampling method. To collect data, Kurdlo's Responsibility Questionnaire (2014), The Adjustment Inventory for School Students (AISS), and Parent-Child Relationship Survey (PCRS) were used. Data analysis was done through structural modeling using Amos24 software. The results revealed that the quality of parent-child relationship mediates the negative relationship between responsibility and adjustment in teenagers in both groups of single-parent mothers and single-parent fathers. In fact, early life experiences with family affect how an individual's subsequent relationships are shaped; thus, strengthening parent-child relationships plays an important role in the growth and development of teenagers, especially single-parent adolescents with special needs.