Gait is one of the examined functions in child development. It should be economical and symmetrical. One test increasingly used by physiotherapists and pediatricians is asymmetrical tonic neck reflex (ATNR). Physiologically, it is observed from in utero up to six postnatal months. This reaction is inhibited with the growing maturation of the central nervous system (CNS). In some children, when the natural process of development is incorrect, ATNR manifests later in life, when it is observed as an automatic response of muscle tension to head rotation. Analysis of pelvis symmetry in the gait of children with active ATNR is important for better understanding their specific movements. In the gait of children with persistent ATNR, some variations are observed. The aim of the study was to investigate the gait symmetry of preschool children and the influence of persistent ATNR. Fifty preschool children with a trace form of ATNR were examined. The distribution of the gait parameters was determined using a BTS G-SENSOR measurement instrument. ATNR negatively influences pelvic obliquity and pelvic rotation (p < 0.01). Younger children have a statistically higher symmetry index of pelvis obliquity in the examined group (p = 0.015). Boys obtain a higher result of symmetry in pelvic tilt than girls in the group (p = 0.027). ATNR affects walking symmetry in preschool children, thus evaluation of the reflex activity and then proper therapy is required to support proper development.