The study aimed to investigate the utilization rates and outcomes of early intervention services on motor development of children with undefined developmental delay, and examine the potential factors associated with children's motor development. A two time period comparison of 129 children with undefined developmental delays was conducted using the data from a developmental assessment unit in a medical center in southern Taiwan from 2011 to 2015. The Peabody Developmental Motor Scales-Second Edition was used to identify the children's motor development. Paired t tests were performed to examine changes in motor status between the two time periods. A logistic regression analysis was conducted to examine the associations between improvements in gross and fine motor development and potential factors. Utilization of early intervention services significantly increased after the initial evaluation from 0% to 92.2%. Approximately, 42.6% of the children showed significant improvement in gross and fine motor development between the two time periods. Normal cognitive development and utilization of occupational therapy services accounted for variability in the improvement of gross motor developmental problems. The crucial indicators of changes in fine motor development were normal cognitive development and preschool attendance. Utilization of early intervention services, such as occupational therapy, was positively correlated with improvements in motor development. It is crucial to offer caregivers comprehensive resources related to early intervention services, especially in regard to motor development.