Rett syndrome (RTT) is a neurodevelopmental disorder characterized by severe dyspraxia, hand stereotypies, and sensory processing issues for which there is no known treatment. This case describes a child with classic RTT and the child's responses to an Ayres Sensory Integration (ASI) treatment intervention (36 one-hour sessions, 3 per week). We coded and analyzed 36 detailed treatment notes to answer the following questions: What strategies and factors facilitated or interfered with participation in the intervention? What critical elements of treatment documentation might detect small changes in praxis and participation? How do patterns of motor or praxis milestones that emerge over time relate to this child's level of participation? We observed an increase in participation when the therapist incorporated elements of neurodevelopmental treatment (NDT) and motor learning theory- treatment strategies commonly used with children who have neuromotor conditions. This increase in participation in the ASI intervention emerged at approximately the same time that the therapist documented acquisition of new motor and praxis skills. We observed the importance of using: lateral movement activities to develop weight-shifting and bilateral coordination, rotary play to increase trunk rotation and improve postural transitions, and rhythm to promote continuing or initiating actions. The documentation of the specific amounts of assistance and prompting needed during treatment sessions was an important tool for tracking small yet meaningful responses to treatment. This case illustrates a novel use of ASI intervention supplemented with strategies that developed foundational skills, and the emergence of praxis and participation in the therapeutic intervention. We suggest further research is needed to determine efficacy of ASI for other children with this rare disorder.