Septic thrombosis of the cavernous sinus (STCS) is an uncommon and potentially lethal disease. Sphenoid and ethmoid sinusitis followed by facial cutaneous infections represents the most common aetiologies, with Staphylococcus aureus as the main responsible organism followed by the Streptococcus pneumoniae. Although all infectious foci of the head and neck area can potentially spread to the cavernous sinus, STCS from oral infection is an exceptionally rare occurrence. We report the unusual case of a patient who presented with an acute STCS secondary to a generalized Streptococcus milleri periodontitis. This case highlights the importance of systematically performing a detailed examination of the oral cavity in patients presenting with intracranial infections caused by uncommon pathogens such as the Streptococcus milleri group.