Thumb and digit-sucking habits or non-nutritive sucking are considered to be the most prevalent among oral habits. Most children stop thumb sucking on their own. If the habit continues beyond 3 to 4 years of age, it not only affects the dental occlusion, but the shape of the thumb/digit may be altered as well. This article presents the management of thumb sucking by modified RURS, elbow guard incorporated with revised 'three-alarm' system. How to cite this article: Shetty RM, Shetty M, Shetty NS, Deoghare A. Three-Alarm System: Revisited to treat Thumb-sucking Habit. Int J Clin Pediatr Dent 2015;8(1):82-86.