Dentin dysplasia is a rare defect of dentin development with an autosomal dominant pattern of inheritance, which is generally divided into 2 main classes based on the clinical and radiographic appearance of the affected dental tissues: type I, which affects the root portion and type II, which affects the coronal portion of the tooth. This paper reports the case of a child aged 10 years and 8 months with both classic and atypical features of dentin dysplasia type I in the permanent dentition. Only few mandibular teeth were affected and presented clinically normal appearing crowns, moderate to severe mobility, short, blunt or almost absent roots. However, no evidence of pulp chamber obliteration or periapical radiolucencies was found. The clinical and radiographic characteristics observed in this patient are different from those reported in the literature, which suggests that this may be a variation of dentin dysplasia type I expression.