The aim of this study was to uncover the possible factors contributing to mandibular anterior crowding in the early mixed dentition. Mandibular dental casts of 60 children in the early mixed dentition were divided into two groups according to the severity of mandibular anterior crowding. The space available for the mandibular permanent incisors, total incisor width, deciduous intercanine width, deciduous intermolar widths, permanent intermolar width, interalveolar width, and total arch length were compared between the crowded group (CG) and noncrowded group (NCG), and correlations with crowding were investigated. The mandibular deciduous intercanine width, mandibular deciduous intermolar widths, mandibular permanent intermolar width, mandibular interalveolar width, space available for the mandibular permanent incisors, and total arch length were significantly larger in the NCG. The total width of the four mandibular incisors did not differ significantly between CG and NCG. Significant inverse correlations were found between crowding and available space, deciduous intercanine width, deciduous intermolar widths, permanent intermolar width, and interalveolar width. Total incisor width was directly correlated with crowding. No significant correlation was found between crowding and total arch length. The results of this study suggested that individual variations play an important role in treatment planning. However, one must not overlook arch length discrepancies and transverse discrepancies in patients with mandibular anterior crowding.