The aim of this study was to assess the effect of bolus calculator function and wireless communication between insulin pump and blood glucose metre on metabolic control in children with type 1 diabetes, treated with insulin pumps. In this randomized, controlled, 12-week trial, 156 patients, aged 12.9 ± 2.6 years, with a history of diabetes of 5.1 ± 3.3 years and glycated haemoglobin values of 7.3 ± 1.2% (56.3 ± 13.44 mmol/mol) were included. Children were assigned to one of three arms: group A, subjects using bolus calculator and wireless communication between insulin pump and blood glucose metre; group B, subjects using bolus calculator without communication between the devices and group C, control group. Devices were downloaded at 0, 6 and 12 weeks. There were statistically fewer episodes of hypoglycaemia in children using bolus calculator compared with the control group: A versus C (3.8 ± 3.1 versus 7.8 ± 5.13 episodes/2 weeks, respectively, p < 0.0001); B versus C (3.6 ± 3.3 versus 7.8 ± 5.1 episodes/2 weeks, respectively, p < 0.0001). Patients in group A used bolus calculator function significantly more frequently than patients in group B (4.9 ± 3.4 versus 2.5 ± 2.9 times/24 h, respectively, p = 0.0006). No significant differences in glycated haemoglobin levels were found between the experimental and the control groups: group A versus C (p = 0.699). The use of bolus calculator did not influence post-prandial glycaemia, body mass index-SD score or insulin/kg/24 h. Bolus calculator use reduces hypoglycaemic episodes independently of communication between insulin pump and blood glucose metre. Wireless communication between devices results in more frequent bolus calculator use.