Objective: to analyze the management of overweight and obesity in children and adolescents by nurses of the Family Health Strategy. Method: this is a study of convergent parallel mixed methods, developed in Health Centers of a municipality in northeastern Brazil. In the quantitative stage, data were collected from a questionnaire applied to 98 nurses and analyzed by descriptive statistics. For the qualitative stage, semi-structured interviews were conducted with seven nurses, interpreted by inductive thematic analysis. The quantitative and qualitative results were integrated and presented by a joint display. Results: most nurses rarely checked waist circumference (77.6%), dyslipidemia (55.7%), blood glucose (42.3%), and neither evaluated blood pressure (75.3%). In the qualitative results, we identified that there are nurses who did not classify body mass index according to sex and age. As for medical tests, the requests were mainly related to the routine of childcare. Guidance on physical activity and diet were given in a basic way or attributed to other professionals, and referrals to other services or professionals were not followed up. Conclusion: it is imperative to train nurses for the management of overweight and obesity in primary care for children and adolescents, with a view to quality of care for the prevention of comorbidities.