Pulsus paradoxus has been defined as a decrease in systolic blood pressure (SBP) of 10 mmHg or more during inspiration. This report describes pulsus paradoxus detected by pulse oximetry during dental procedure. Case: A 10 years old boy who had impacted mandibular premolar with malformation scheduled for extraction under intravenous sedation with Fentanyl and Propofol. The patient showed upper airway obstruction with stridor and pulsus paradoxus. Though pulsus paradoxus is generally critical condition, in this case, respiration and other vital sign was maintained comparatively well with care in administering oxygen and considerate monitoring of pulse oximetry and capnography. Discussion: Noninvasive continuous monitoring of pulse oximetry allows recognition of pulsus paradoxus which can lead to serious problems. Clinicians should know very well about it and be able to manage of this kind of situation.