Bad breath or foul-smell breath (cacosmia) has many causes. The sources may originate from the nose, mouth, lungs, or even digestive tract. Sinusitis is among the commonest nasal causes which may remain undetected for a long time. As our smell sensation adapts easily, the persons affected may not notice the bad smell until being told by someone's in close proximity. Underlying malignancy and fungal infection needs to be ruled out. Endoscopic sinus surgery was performed and healed nicely.