The present study sought to develop a comprehensive family-centered program of enhancing sensorimotor functions and evaluate its effectiveness in muscle stiffness and motor skills of slow-paced children with Down syndrome. This quasi-experimental research had a pretest-posttest control group design with a follow-up session.  The statistical population of the study was comprised of all mothers of 4- to 7-year-old children with autism spectrum disorder in Kashmar in 2018-2019 who had been referred to Sa’adat and Ava Rehabilitation Centers. First, Peabody Developmental Motor Scale (Folio & Fewell, 1983) and Ashworth Scale of Muscle Spasticity  (1964) were given to the parents as the pretest. Then, among those who had gained low scores on the tests, 20 individuals were selected as the sample by convenience sampling method and were randomly assigned to experimental (N=10) and control (N=10) groups. The experimental group underwent family-centered treatment sessions to enhance sensorimotor functions, whereas and the control group did not receive any intervention. Next, both groups were post-tested using the research instruments and a follow-up test was conducted after a month. The collected data were analyzed using SPSS-22 software and ANCOVA. Results revealed that the comprehensive family-centered program of enhancing sensorimotor functions was effective in increasing muscle strength and motor skills of slow-paced children with Down syndrome (p <0.05). Hence, this program can be utilized to improve motor skills of children with Down syndrome.