Background: Tuberculosis is a major global public health challenge and disease in young children is particularly severe. Diagnosing tuberculosis in children is complex as clinical presentation is often atypical and available diagnostic modalities are imperfect. Diagnosis is particularly challenging in developing countries where resources and access to sophisticated facilities are limited. The South African primary health care system requires frontline nurses to be equipped to suspect, diagnose and treat children with tuberculosis, but their capacity to diagnose childhood tuberculosis is unknown. Relatively low rates of childhood tuberculosis notification suggested that tuberculosis may have been under-diagnosed in Mpumalanga Province. Objective: To determine the ability of the primary health care nurses to diagnose childhood tuberculosis in primary care public health facilities in Gert Sibande District, Mpumalanga Province. Methodology: Within-method triangulation by means of a self-completed questionnaire and a facility audit of records and diagnostic aids, was used to assess nurses' knowledge and determine whether primary health care facilities were adequately equipped to facilitate the diagnosis of childhood tuberculosis. Results: There was a limited appreciation of the need to use complementary clinical and epidemiological features and diagnostic approaches to diagnose childhood tuberculosis. Child contacts had only been screened in 22.6% (111/491) of confirmed smear positive adult tuberculosis cases reviewed. The diagnostic score chart advocated by the World Health Organization and South African Department of Health was only used by 16% (10/62) of the facilities. Nurses who had been specifically trained on tuberculosis were more knowledgeable about diagnostic approaches and all respondents who were using the score chart had received specific tuberculosis training. Conclusion: The deficiencies in knowledge and practice evident during this survey and practice audit could at least partially explain the relatively low detection rates of childhood tuberculosis in Gert Sibande district, Mpumalanga Province. There is a need to equip primary health care nurses with the knowledge, support and access to diagnostic tests required to ensure a high index of suspicion and early, effective, diagnosis of tuberculosis in children.