Background: Pneumocephalus is a common complication presented as air in the cranial cavity after cranial surgery. We present a very rare case of isolated new onset aphasia due to pneumocephalus after evacuation of subdural hematoma (SDH). Tension pneumocephalus presenting as isolated aphasia has not been reported earlier although associated paresis has been reported. Case presentation: We present the case of a 13-year-old male child with a history of fall before the onset of symptoms like headache and vomiting. The immediate MRI of the brain showed left-sided frontotemporoparietal subacute SDH with significant midline shift and subfalcine herniation. The child was subsequently managed with craniotomy and evacuation of hematoma with duraplasty. The patient developed aphasia on second-day postsurgery which progressed from moderate to severe aphasia by day 4. Computed tomography (CT) scan revealed pneumocephalus and an increase in the pneumocephalus in imaging on post-op day 4 with no other abnormalities. The condition was then managed by removing the subgaleal drain and administering high flow oxygen of 10 l/min. Conclusion: This case signifies the importance of proper diagnosis of new-onset neurological deficits after evacuation of subdural hematoma for the better outcome.