Ankle-foot orthoses (AFOs) are intended to improve toe clearance during swing and ankle position at initial contact (IC) and midstance. Changes that lead to improved ankle-foot kinematics may result in a more biomimetic roll-over shape (ROS). ROS is the effective geometry to which the ankle-foot complex conforms between IC and contralateral IC. An effective ROS during gait may facilitate forward progression. This study investigated the effect of an AFO on ROS in adults with hemiplegia following stroke. Kinematic and force data were recorded from 13 people with hemiplegia and 12 controls. Hemiplegic subjects walked at a self-selected speed with and without an articulated AFO with plantar flexion stop. For the involved limb, the AFO significantly increased the ROS arc length (from 32.6% to 55.7% of foot length [FL]) and arc radius (67.4% to 139.3% of FL) and significantly altered the sagittal plane location of the first center of pressure (COP) point, moving it posterior to the ankle center (-1.2% to -20% of FL) (p < 0.002 for all comparisons). However, when hemiplegic patients walked with an AFO, their mean arc radius was greater, mean arc length less, and the first COP point further posterior than those of control subjects.