To assess Sweet Talk, a text-messaging support system designed to enhance self-efficacy, facilitate uptake of intensive insulin therapy and improve glycaemic control in paediatric patients with Type 1 diabetes. One hundred and twenty-six patients fulfilled the eligibility criteria; Type 1 diabetes for > 1 year, on conventional insulin therapy, aged 8-18 years. Ninety-two patients were randomized to conventional insulin therapy (n = 28), conventional therapy and Sweet Talk (n = 33) or intensive insulin therapy and Sweet Talk (n = 31). Goal-setting at clinic visits was reinforced by daily text-messages from the Sweet Talk software system, containing personalized goal-specific prompts and messages tailored to patients age, sex and insulin regimen. HbA(1c) did not change in patients on conventional therapy without or with Sweet Talk (10.3 +/- 1.7 vs. 10.1 +/- 1.7%), but improved in patients randomized to intensive therapy and Sweet Talk (9.2 +/- 2.2%, 95% CI -1.9, -0.5, P < 0.001). Sweet Talk was associated with improvement in diabetes self-efficacy (conventional therapy 56.0 +/- 13.7, conventional therapy plus Sweet Talk 62.1 +/- 6.6, 95% CI +2.6, +7.5, P = 0.003) and self-reported adherence (conventional therapy 70.4 +/- 20.0, conventional therapy plus Sweet Talk 77.2 +/- 16.1, 95% CI +0.4, +17.4, P = 0.042). When surveyed, 82% of patients felt that Sweet Talk had improved their diabetes self-management and 90% wanted to continue receiving messages. Sweet Talk was associated with improved self-efficacy and adherence; engaging a classically difficult to reach group of young people. While Sweet Talk alone did not improve glycaemic control, it may have had a role in supporting the introduction of intensive insulin therapy. Scheduled, tailored text messaging offers an innovative means of supporting adolescents with diabetes and could be adapted for other health-care settings and chronic diseases.