We describe a rare case of deep vein thrombosis (DVT) in children, highlight the importance of early diagnosis of rare disease with potential complications. In a 5 year old boy presented with persistent leg pain without any obvious cause. Detailed investigation led to diagnosis of DVT. As there are common differential diagnoses for leg pain in children, pediatricians usually have a low index of suspicious of DVT in children. This case highlight that paediatricians must consider DVT in their differential diagnosis when children present with leg pain.