Background: Chemotherapy-induced thrombocytopenia (CIT) is a significant complication of cancer therapy. Data on the optimal management approaches of this morbidity in children and young adults are still limited.

Aim: The aim of the study is to estimate the frequency and severity of CIT and associated clinically significant bleeding in children and young adults with solid tumours and haematologic malignancies.

Methods: For this retrospective, hospital-based study, children (0–18 y) and young adults (19–40 y) with different types of solid tumours and haematologic malignancies who received chemotherapy at the Muratsan Hospital Complex of Yerevan State Medical University were identified from the patients’ database and included in the study (overall 122 patients). Thrombocytopenia was defined as a decrease of platelet count below <100 × 109/L. For assessing bleeding, WHO scale had been used.

Results: Overall, the whole group of patients received 430 chemotherapy cycles. During 131 (31.6%) chemotherapy cycles, patients developed CIT. The study revealed a statistically significant inversely proportional correlation between the age and the severity of CIT. Another important finding of the study was that the patients, who previously were exposed to radiation therapy, were more likely to develop CIT, than those who have not received radiation therapy (68% and 28.7%, p = 0.001). From 430 cycles of chemotherapy, 31 (7.2%) cycles reported to have bleeding events.

Conclusion: Our study showed that clinically significant thrombocytopenia and bleeding are quite rare among children and young adults. Younger age and previous exposure to radiation therapy are positively correlated with the severity of thrombocytopenia. Larger studies are needed to investigate these findings.