Endoscopic frontal sinus surgery requires special attention to the numerous anatomical variations. Additionally, in situations of revision surgery, endonasal frontal sinus identification may be challenging. Numerous strategies have been described to access the frontal sinus in endonasal endoscopic frontal sinus surgery including an additional external approach. A pilot study is presented using a newly designed modular mini-endoscope (1.1 mm, 10.000 pixel, 2 working channels and 120° lens) to assist the frontal sinus surgery through a transcutaneous puncture of the frontal sinus. We used this mini-endoscope for primary frontal sinus surgery on 3 patients and for revision frontal sinus surgery on 4 patients. In all patients, the mini-endoscope could be placed in the frontal sinus without side effects. The visible illumination at the frontal sinus floor, caused by the mini-endoscope being in the frontal sinus, guided the surgeon endonasally directly to the frontal sinus floor. Frontal sinus drainage was achieved by the described guidance on all patients. In conclusion, mini-endoscopy of the frontal sinus might be an interesting option in endoscopic frontal sinus surgery to guide the surgeon by illumination in complex anatomical situations to the frontal sinus. This technique will contribute to further improvement in endonasal endoscopic frontal sinus surgery.