Practices for promoting a child’s best interests in rehabilitation are not sufficiently understood. This study describes the practices from the perspectives of professionals and parents of children with disabilities. We conducted 11 interviews: 5 in focus groups with professionals ( n = 27 [69%]), 3 with parents ( n = 9 [23%]), and 3 individual interviews of paediatric neurologists ( n = 3 [8%]). We used a qualitative approach, which included inductive content analysis, to examine the transcribed interview data. The practices for promoting a child’s best interests consisted of collective framing of child-specific rehabilitation, fostering a fulfilling daily life for the child, and ensuring appropriate rehabilitation. This was enhanced by using child-specific practices and comprehensively understanding the child’s rehabilitation in everyday life but was hindered by the absence of an established process and guidelines. The results highlighted substantial challenges in collaboration aligned with the child’s best interests, enabling the child’s active participation, and addressing the individual needs of the child and family. Promoting best interests through family–professional partnerships by using a systemic and ecological approach could guide the rehabilitation process and ensure the child’s right to participate.