The aim of this study is to assess the impact of the internet-based upload blood glucose monitoring and therapy management system (Carelink(®)) in patients with type 1 diabetes. Diabetic patients treated with pump infusion for ≥3 months were prospectively randomized to use the CareLink(®) with (4 months) and without (4 months) diabetes-team initiated contact (n = 36, intervention group) or to continue standard care for 4 months and then transfer to the CareLink(®) without diabetes-team initiated contact (n = 34, control group). In the first 4 months, treatment was adjusted monthly by the same team in both groups. Main outcome measures were HbA1c level and scores on the Diabetes Treatment Satisfaction and Diabetes Quality of Life Questionnaires. Patients who submitted <3 times during each 4-month segment were considered noncompliant. Mean patient age was 14.02 ± 5.33 years; mean diabetes duration, 6.4 ± 4.7 years; median duration of pump treatment, 2.5 years. After 4 months, mean HbA1c level decreased from 8.75 ± 0.84 to 8.45 ± 0.90% in the intervention group (p = 0.013) and from 8.65 ± 0.57 to 8.37 ± 0.73% in the control group (p = 0.054). Within the intervention group, the difference in the change in HbA1c levels between compliant and noncompliant patients was significant (8.17 ± 0.81 vs. 8.99 ± 0.85%, p = 0.017). Only in the compliant subgroup was the decrease from baseline significant (p = 0.006). Similar findings were noted in the control group at 8 months (p < 0.05 and p = 0.018, respectively). There were no significant changes in questionnaire scores at 4 or 8 months in either group. Use of the CareLink(®) system is associated with significantly improved glycemic control in compliant patients, with no apparent effect on patient satisfaction or quality of life.