Purpose This study aimed to increase our understanding of the psychosocial well-being of young adult childhood cancer survivors (YACCS) as well as the positive and negative impacts of cancer. Methods YACCS (aged 18–30, diagnosed ≤ 18, time since diagnosis ≥ 5 years) cross-sectionally filled out the “Pediatric Quality of Life Inventory Young Adults” (PedsQL-YA), “Hospital Anxiety and Depression Scale” (HADS), and “Checklist Individual Strengths” (CIS-20R) to measure fatigue and survivor-specific “Impact of Cancer - Childhood Survivors” (IOC-CS), which measures the long-term impact of childhood cancer in several domains. Descriptive statistics (IOC-CS), logistic regression (HADS, CIS-20R), and ANOVA (PedsQL-YA, HADS, CIS-20R) were performed. Associations between positive and negative impacts of childhood cancer and psychosocial outcomes were examined with linear regression analyses. Results YACCS ( N  = 151, 61.6% female, mean age 24.1 ± 3.6, mean time since diagnosis 13.6 ± 3.8) reported lower HRQOL (− .4 ≤  d  ≤ − .5, p  ≤ .001) and more anxiety ( d  = .4, p  ≤ .001), depression ( d  = .4, p  ≤ .01), and fatigue (.3 ≤  d  ≤ .5, p  ≤ .001) than young adults from the general Dutch population. They were at an increased risk of experiencing (sub)clinical anxiety (OR = 1.8, p  = .017). YACCS reported more impact on scales representing a positive rather than negative impact of CC. Various domains of impact of childhood cancer were related to psychosocial outcomes, especially “Life Challenges” (HRQOL β  = − .18, anxiety β  = .36, depression β  = .29) and “Body & Health” (HRQOL β  = .27, anxiety β  = − .25, depression β  = − .26, fatigue β  = − .47). Conclusion YACCS are vulnerable to psychosocial difficulties, but they also experience positive long-term impacts of childhood cancer. Positive and negative impacts of childhood cancer were associated with psychosocial outcomes in YACCS. Screening of psychosocial outcomes and offering targeted interventions are necessary to optimize psychosocial long-term follow-up care for YACCS.