Children with hand motor impairment due to cerebral palsy, traumatic brain injury, or pediatric stroke are considerably affected in their independence, development, and quality of life. Treatment conventionally includes task-oriented training in occupational therapy. While dose and intensity of hand therapy can be promoted through technology, these approaches are mostly limited to large stationary robotic devices for non-task-oriented training, or passive wearable devices for children with mild impairments. Here we present PEXO, a fully wearable actuated pediatric hand exoskeleton to cover the special needs of children (6 to 12 years of age) with strong impairments in hand function. Through three degrees of freedom, PEXO provides assistance in various grasp types needed for the execution of functional tasks. It is lightweight, water proof, and inherently interacts safely with the user. It meets mechanical requirements such as force, fast closing movement, and battery lifetime derived from literature and discussions with clinicians. Appealing appearance, user-friendly design, and intuitive control with visual feedback of forearm muscle activity should keep the user motivated during training in the clinic or at home. A pilot test with a 6-years old child with stroke showed that PEXO can provide assistance in grasping various objects weighing up to 0.5 kg. These are promising first results on the way to make hand exoskeletons accessible for children with neuromotor disorders.