To identify radiological findings of diaphragmatic mesothelial cysts (DMC) in the pediatric age group and to assess follow-up outcomes. In this study, 27 pediatric age group patients were evaluated with ultrasonography (US), computed tomography (CT), or magnetic resonance imaging due to various clinical indications and diagnosed with DMC from May 2014 to September 2018. Age, sex, imaging indications and DMC localization, volumes in the first diagnosis, and follow-ups were retrospectively evaluated. Descriptive statistics were used for age, sex, imaging indications, and volume are presented as numbers and percentages. Ages range from 5 months to 13 years. Nine girls and 18 boys included in this study. The most common imaging indications were abdominal pain, diarrhea, and obesity. The mean volume of DMC was at first 2.62 and 2.45 mL during the follow-ups. There was volume reduction in 24 cases, and no change in 3 cases. Mean follow-up duration was 22.4 months. The US imaging findings were similar for all cases, bilobular cystic lesion with fat indentation between the cyst and liver parenchyma. The typical localization and lateral fat sign are useful in differential diagnosis of DMC from cystic lesions of liver. The US is a very effective and beneficial radiological method for diagnosis and follow-up. Routine clinical and sonographic follow-ups may be sufficient for asymptomatic patients with stable cyst volume.