This descriptive correlational study determined symptom prevalence, characteristics and distress in a sample of 54 children newly diagnosed with cancer in a paediatric oncology inpatient department and its associated outpatient clinics in Izmir, Turkey. Data were collected using the Memorial Symptom Assessment Scale 1, 2 and 3 months after diagnosis. Demographic data were collected using a questionnaire developed by the researchers while information on respondents' disease status and treatment regimens was obtained from medical records. Cluster analysis techniques were used to identify symptom clusters in the sample. The study identified a number of symptom clusters affecting children or adolescents (age range 10 to 18 years), although different clusters became apparent at each data collection point. The most common symptoms in newly diagnosed respondents were lack of appetite, nausea, lethargy, hair loss and feelings of sadness. Four symptom clusters were apparent 1 month after diagnosis, five in the second month and four in the third month. The study demonstrated that respondents experienced a wide range of symptoms in the months immediately following a cancer diagnosis and the start of treatment, which are findings that can be used to develop clinical guidelines for symptom assessment and management in children and adolescents with cancer.