The diagnosis of sinus pathologies remains a challenge due to their complex anatomy and the diagnostic limitations of traditional imaging techniques. To report the outcome and limitations of a recently developed minimally invasive sinoscopic technique (MIST), using a 2 mm diameter and 18 cm long easily portable endoscope, in clinical cases with suspicion of paranasal disease. Horses admitted between July 2018 and 2020 that received the MIST. The technique evaluated the frontal, caudal maxillary, and sphenopalatine sinuses in eight horses and also the rostral maxillary and conchal ventral sinuses in 3/8. The technique was considered useful for case management (ruled out sinus involvement (2/8), obtained a definitive diagnosis (2/8) or guided surgical approach (3/8)) in 7/8 cases. Visualization was limited in one horse presenting inspissated pus in all sinus compartments. No significant intra- or post-MIST complications were encountered. The reported technique is quick and simple to perform but requires performance in precise landmarks, knowledge of sinus anatomy, and having specialized equipment. Surgeons and practitioners without access to CT, working in an ambulatory setting and/or looking for a simpler sinoscopic technique could benefit from this technique. The technique has shown value to either obtain a diagnosis or guide treatment but also as a screening technique. Price of the equipment, the flexible endoscope lacks a control knob or a flush system, and limited case numbers to date. The MIST involves a less invasive approach and is performed rapidly and with a lower cost to clients although specialized portable equipment is required.