Introduction: Type 1 Diabetes Melitus (T1DM) treatment is demanding, due to daily blood glucose monitoring, certain diet plan, specific exercise program, multiple daily insulin injections, and management of episodes of hypo- or hyperglycemia. Family conflict may play a significant role in the adherence of adolescents with type 1 diabetes. Purpose: To evaluate Greek families’ conflicts and determine their relationship with T1DM adolescents’ adherence. Methods: A cross-sectional study was conducted from October 2021 to June 2022. Due to COVID-19 restriction, all the interviews were conducted through online survey. Three questionnaires were distributed to the adolescents. Pediatric Quality of Life Inventory tool, Diabetes Self-Management Profile and Collaborative Parent Involvement Scale for Youths Questionnaire. PeDsQL was distributed to their parents as well. Results: 59 adolescents (N=21) aged 10-19 years and their parents (N=38) participated. The mean values of PedsQL for all five factors ranged from 55.7 (Worry subcategory) to 77.8 (Treatment adherence), showing an overall moderate QoL. According to the mean values, parents’ perspectives PedsQL for all five factors ranged from 38.6 (Worry subcategory) to 77 (Treatment adherence), showing an overall moderate QoL. Mean DSMP score indicated a high level of adherence of children with diabetes mellitus to their treatment, whilst mean cooperation score indicated a high level of cooperation between parents and adolescents with T1DM and low level of FC. Bivariate analysis revealed that less FC was related to better treatment adherence in adolescents. Conclusions: T1DM management remains challenging, particularly as children grow older and move into adolescence. The family can play a significant role in T1DM management. Diabetes multidisciplinary teams should evaluate and understand family members' interactions detecting inter-family problems such as high frequency of FC. Provision of family support can improve communication between adolescents and parents and may reduce FC resulting in better T1DM treatment adherence and outcomes.