Objective: To identify the most effective form of contact, as a possible intervention to reduce absenteeism in consultations of children with suspected or confirmed pulmonary tuberculosis. Methods: A randomized clinical trial was conducted with prospective data collection, between March 2017 and February 2018. Patients were randomized into three groups to be reminded about the appointment: telephone contact, SMS or WhatsApp, or no intervention. A convenience sample was obtained, with a significance level of 5%. Results: 78 children were included, with a median age of four years old (zero to 14); 59.0% of them were in treatment for a latent infection and 6.4% had active tuberculosis. Among the 78 children, 74.4% lived in Curitiba (Sourhern Brazil); 62.8% lived with both parents; 38.5% of the parents had formal employment and 47.4% of the mothers were housewives; 50.8% of the fathers and 55.7% of the mothers had more than nine years of schooling. In 78.2% of the families, per capita income was up to 0.5 minimum wages; 27.3% were enrolled in social programs; 28.2% lived in homes provided by the government. There was a total of 238 interventions made: 85 (35.7%) by telephone contact, 78 (32.8%) by text message (WhatsApp was 97.2% of these) and 75 (31.5%) had no further contact. There was no statistical difference among the sociodemographic and cultural characteristics studied. The absenteeism rate was 24.0% and the abandonment rate was 16.7%. Giving a reminder to the patient’s guardian prior to the consultation, regardless of the intervention (p=0.021) and specifically by WhatsApp message (p=0.032) was associated with no absenteeism, though it was not associated with abandonment of the treatment. Conclusions: Using new tools, such as WhatsApp, to remind guardians of appointments reduces absenteeism. Consequently, it may lead to a reduction in abandoning treatment and it may improvetreatment outcome of children with a tuberculosis infection or disease.