The pericranial flap is a well-vascularized, robust flap that is used to reconstruct anterior skull base defects following resection of skull base tumors. Failure of this flap is uncommon. However when it occurs, the consequences are potentially disastrous and it poses a challenge to further reconstruction. The authors report the first patient of onlay pericranial flap breakdown following endoscopic craniofacial resection. Possible contributing factors are identified and further management is discussed. With the endoscopic approach being increasingly utilized for craniofacial resection, it is imperative to be mindful of these factors to minimize the risks of onlay pericranial flap failure.