This study examined the influence of single-parent families’ residential environment on adolescent children’s Internet addiction during the COVID-19 pandemic, together with the mediating effects of single parents’ depression and parenting stress. A representative sample from the raw data of the Survey of Single-parent Families in 2021 was used, and main variables were measured with scales included in the survey. Direct and indirect influences of residential environment were analyzed by utilizing Model 6 of the Process Macro. The following results were yielded from data analyses. First, single-parent families’ residential environment had a negative influence on adolescent children’s Internet addiction. Second, single parents’ depression had a simple mediation effect on the influence of residential environment on Internet addiction. Third, single parents’ parenting stress did not have a simple mediation effect. Finally, single parents’ depression and parenting stress had a dual mediation effect. That is, the level of residential environment decreased the level of depression, which in turn decreased the level of parenting stress and finally decreased the level of Internet addiction. This study has a point of contribution in that it examined the influence of single-parent families’ residential environment on the development of adolescent children and mechanisms behind the influence. Diverse strategies to support the healthy development of adolescents in single-parent families were discussed based on the findings of this study.