Active and passive mouth opening exercises are a very common practice in oral and maxillofacial surgery especially for various conditions causing limited mouth opening like space infections, trauma, and ankylosis. But most of the practitioners do not follow basic principles while advocating these active mouth opening exercises and also take it for granted that it would benefit the patient in the long run. Because of this, the mouth opening physiotherapy by itself can at times lead to unwanted complications. We report a case wherein due to active physiotherapy, the patient had complications leading to persistent temporal space infection which required surgical intervention and hospitalization. This could have been because of hematoma formation during physiotherapy which got infected due to anchoretic infection of unknown etiology and resulted in temporal space infection. Hence, our conclusion is that whenever mouth opening exercises are initiated, it should be done gradually under good antibiotic coverage to avoid any untoward complications and for optimum results. According to the current English literature, such a complication has not been documented before.