A randomized, controlled trial was conducted to determine the effect of Pilates-based exercise on postural alignment. Seventy-four adult women (mean age ± SD, 34.9 ± 16.4 years) were randomized to a Pilates-based mat class (n = 40) or a control group (n = 34). Pilates-based exercise participants were taught the Initial Mat of Body Control Pilates for 6 months, twice a week, for 60 minutes per session; the control group received no exercise intervention. Repeated measurements were performed at baseline, 3 months, and 6 months of the frontal alignment of the thoracolumbar spine, shoulder, and pelvis, and sagittal alignment of the head and pelvis. No differences were found in either group, over time, on frontal alignment of the thoracolumbar spine and pelvis. The experimental group showed significant improvements in frontal alignment of the shoulder and sagittal alignment of the head and pelvis at 6 months. The Pilates-based exercise enhanced some parameters of the postural alignment of women, as measured by frontal alignment of the shoulder and sagittal alignment of the head and pelvis. The significant improvement in sagittal alignment of the head may imply that 6 months of Pilates-based exercise enhances sagittal alignment of the cervical or thoracic spine.