The aims of the study were to examine the reliability and validity of six minutes walking test (6MWT) in children with intellectual disabilities and to identify its relationship with anthropometric measurements. 40 students with intellectual disabilities (Age: 12.1±1.8 years, Height: 136.6±12.0m, Body Mass: 34.5±13.4 ) participated in this study. All participants performed Kg, BMI: 18.0±4.9 kg/m2 6MWT twice at least one day apart to study its reliability. They also performed Countermovement Jump (CMJ) and Free Countermovement Jump (FCMJ) to examine their relationship to 6MWT. In order to study the Construct validity of the 6MWT, the participants were divided into two groups according to their degree of intellectual disability (simple disability = 21 and moderate disability = 19). Results demonstrated an acceptable reliability of the 6MWT through applied statistical tools (Intraclass Correlation Coefficient= 0.857, Standard Error of Measurement = 15.8m, Minimum Detectable Change= 43.8m, Limits of Agreement = 112.9±16.1m). The area under the receiver operating characteristic (ROC) curve was 0.742 which means that the test has the capacity to distinguish between students with simple and moderate intellectual disability. Significant correlations were recorded between 6MWT and both CMJ and FCMJ (r=0.484, p=0.002; r= 0.417, p=0.007, respectively). On the other hand, no significant correlation was observed between 6MWT and all the anthropometric measurements. The findings of the current study indicate the reliability and validity of 6MWT and the possibility of using it on a widespread level in the field of the assessment of functional capacity of children with intellectual disabilities.