During the COVID-19 lockdown, with social distancing measures in place and a decrease in social activities, emotional states are more likely to be transferred between family members via increased interactions and communication. However, longitudinal evidence, particularly for early adolescents, is lacking. This study investigated family pre-pandemic influences on parental stress and adolescent psychosocial wellbeing during the COVID-19 pandemic. Data were collected from 233 adolescents and their parents before and during the initial phase of the pandemic. Parents reported their own stress level and perception of adolescent adjustment problems, whereas adolescents reported their own psychological distress level. In addition, adolescents also reported their satisfaction with family life in the pre-pandemic survey. Cross-lagged path models indicated reciprocal associations between parental stress and perception of adolescent adjustment problems. Compared to adolescents low in pre-pandemic family life satisfaction, those adolescents with higher levels of family life satisfaction before the pandemic reported lower levels of anxiety and stress only when parental stress showed no increase during the pandemic. Findings provide support for the mutual influences between parental stress and perceived adolescent adjustment problems during the pandemic. Special attention should be paid to those adolescents who undergo significant family life changes during the pandemic.