Background The study aimed to assess accuracy, satisfaction and usability of a flash glucose monitoring system (FGM) in children and adolescents with type 1 diabetes mellitus (T1DM) attending a diabetes summer camp. Methods Sixty‐six children and adolescents with T1DM aged 6 to 17 years participating in a 7‐day medically supervised summer camp were enrolled. Capillary blood glucose (BG) and flash glucose (FG) values were measured simultaneously at breakfast, lunch, and dinner and for any given FG value <72 mg/dL (<4.0 mmol/L) during daytime, <108 mg/dL (<6.0 mmol/L) at nighttime, >270 mg/dL (>15.0 mmol/L) or when patient symptoms were discordant with sensor readings. Sensor‐related issues were documented and patients' and healthcare professionals' (HCPs) satisfaction was evaluated. Results FGM demonstrated satisfactory clinical accuracy compared to reference capillary BG values with 98.8% of values falling within the clinically acceptable zones (A and B) of the consensus error grid. Overall mean absolute relative difference (MARD) was 16.7% ± 16.1%. Specific calculations of mean absolute difference (MAD), mean relative difference (MRD), and mean difference (MD) demonstrated that FGM overestimated BG values across all glycemic ranges. Overall satisfaction with the FGM was high in 91.7% participants and 95.0% HCPs, although confidence in the system was low in 18.0% participants and 40.0% HCPs. Conclusions The FGM exhibited satisfactory clinical accuracy. However, based on the present data, we conclude that no decision should be taken on the basis of a single, non‐verified, FGM value alone. Our study highlights the need for revised therapeutic education for patients/families and further investigation on the integration of sensor readings in clinical decision‐making.