Objective The association between diet quality, dietary behavior and health-related quality of life has been mostly examined in children and adolescents with specific chronic diseases. No systematic review has synthesized the influence of diet quality and dietary behavior on health-related quality of life in the general population of children and adolescents. The purpose of this study was to systematically review the primary studies that evaluated the association between diet quality, dietary behavior and health-related quality of life in the general population of children and adolescents and to synthesize the findings for the association. Methods A computer search in the databases of MEDLINE, EMBASE and PSYCINFO was performed to retrieve English language studies that were published from 1946 up to April 8, 2018. We also screened the PubMed-related articles and the reference lists of the existing relevant literature to identify other eligible studies. We synthesized the association between diet quality, dietary behavior and health-related quality of life using both a qualitative method and meta-analysis. We reported the review following up the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guideline. Results Seventeen studies were included in the synthesis including twelve cross-sectional studies and five longitudinal studies. We found that diet quality and dietary behavior were associated with health-related quality of life in children and adolescents. The positive effect of healthy diets on health-related quality of life was observed for multiple domains of health-related quality of life, including physical, school and emotional functioning, and psychosocial quality of life. We observed a dose–response relationship between the diet exposure and health-related quality of life, where an unhealthy dietary behavior or lower diet quality was associated with decreased health-related quality of life among children and adolescents. Conclusion The findings of the systematic review suggest the importance of promoting healthy diets and nutrition for good health-related quality of life among children and adolescents. Future research is needed to strengthen the evidence for prospective relationships and for the dose–response effect between diet quality, dietary behavior and health-related quality of life among children and adolescents.