Background The burdens of type 1 diabetes management in adolescence adversely affect their quality of life, reduce adherence to diet, and worsen metabolic control. Parental monitoring can play a protective role in adolescent diabetes management. Aim This study was conducted to determine the effects of parental monitoring on quality of life and diet quality in adolescents in diabetes care. Material and methods 100 adolescents (52 males, 48 females) with type 1 diabetes aged 13-18 years and their parents participated in the study. The parental monitoring of diabetes care scale (PMDC) in adolescents with type 1 diabetes was used to evaluate parental monitoring. PedsQL (TM) (Pediatric Quality of Life Inventory) Diabetes Module Version 3.0 was used to assess quality of life. Three-day retrospective food intake records were collected from the adolescents with type 1 diabetes, and diet quality was evaluated with the Healthy Eating Index-2010 (HEI-2010) calculated from data obtained from food intake records. Results Statistically significant and one-sided correlations were identified between the PedsQL total scale and subscale scores of adolescents with type 1 diabetes and the scores of the parental monitoring of diabetes care scale (r = 0.437 and p < 0.001). Statistically significant and one-sided correlations were found between some subcomponents of diet quality, i.e., dark leafy greens and dried legumes, whole grains, dairy products, fatty acids, and total HEI levels, and parental monitoring of diabetes scale scores (r = 0.321 and p < 0.001). When HbA1c levels remained constant in adolescents with type 1 diabetes, each 10-point increase in the parental monitoring of diabetes care scale increased the total HEI level by 0.68 points (95% CI: 0.20-1.16). Conclusions As parental monitoring increases in adolescents with type 1 diabetes, the diet quality and quality of life of adolescents with diabetes also increase.