Facial penetrating injuries can cause retention of foreign bodies in the frontal sinus. This rare condition can remain underdiagnosed for years, since non-specific symptoms, such as headaches and nasal obstruction, can be developed. So far, removal by an endoscopic approach is the most preferred treatment option because it is less invasive with a short recovery time. However, removal by an open surgical approach remains the method of choice for large foreign bodies, especially in cases of coexistent non-reducible fractures of the anterior table of the frontal bone. We present a case where a combined approach - open and endoscopic - was necessary to successfully remove a retained foreign body from a frontal sinus. With the assistance of a transnasal endoscope, the retained stone was mobilized and removed from the open frontal sinus followed by osteosynthesis of the anterior table. Therefore, in special circumstances, a combination of both techniques should be considered for the optimal outcome.