The global COVID-19 pandemic has had an unprecedented psychological effect on young people. The current study aimed to examine the associations between parent-child relationships (parental involvement and parental warmth) and, depression, anxiety, stress and flourishing during emerging adulthood in Spain before (2015) and during (2020) the COVID-19 pandemic. The research compares 2828 emerging adults aged between 18 and 29 years from two different cohorts. Every cohort was comprised for two samples. Sample 1-Cohort 1 and Sample 1-Cohort 2 were collected at U. Osuna and Sample2-Cohort 1 and Sample 2-Cohort 2 were collected at U. Sevilla. Regarding the Sample 1-Cohort 2 was recruited in spring 2020, before the lockdown and Sample 2-Cohort 2 on autumn 2020 during Covid crisis. In the Cohort 1 participants were 1301 emerging adults (59.1% women, 40.9% men; M = 20.06, SD = 2.03) and Cohort 2 participants were 1527 emerging adults (64% women, 35.4% men and 0.6% others; M = 20.48, SD = 2.48). Result showed stability in family relationships variables between 2015 and 2020 pre-pandemic sample (both samples 1) but a decrease in parental involvement and parental warmth between 2015 and 2020 covid-19 sample (samples 2). Parental involvement and parental warmth showed negative and significantly associations with depression, anxiety and stress and positive one with flourishing for both cohorts. Furthermore, the associations between parent-child variables and depression, anxiety, stress and flourishing were generally stronger in Cohort2 (2020) than in Cohort1 (2015), both for Samples 1 and Samples 2. These findings revealed that high-quality parent-child relations continued to be a protective factor against mental illness among emerging adults even under adverse conditions as those experienced during COVID-19 pandemic when family relationships is deteriorated. It is necessary to develop psychological interventions aimed at fostering the protecting role of family to promote the emerging adults’ psychosocial wellbeing.