Background: Reliability of an instrument or clinical test should be known in the field of rehabilitation medicine. But the reliability of most of clinical test to be used among pediatric population with disabilities is yet to be known. One among them is the timed standing balance test. Aim: To determine the minimal detectable change at 95% confidence (MDC95) for the static and dynamic standing balance test in children with Down syndrome (DS). Methods: A sample of nine (09) children with DS, aged between 8 and 17 years were recruited randomly from the recognized special school. Children with DS who were able to understand and obey simple commands were selected and noted their anthropometric measurements. Standing balance was assessed using timed unipedal stance on a hard floor for static and on foam with uniform density for dynamic balance. Standing balance was assessed thrice with an interval of minimum two (02) days in four conditions, Eyes Open Static (EOS), Eyes Closed Static (ECS), Eyes Open Dynamic (EOD) and Eyes Closed Dynamic (ECD) to estimate test retest reliability, Intraclass correlation coefficient (ICC). Then standard error of measure (SEM) and minimal detectable change (MDC95) was calculated. Results: Test retest reliability in four conditions, EOS, ECS, EOD and ECD are ICC = 0.93, 0.91, 0.92 and 0.91 respectively while 1.27 s, 1.63 s, 0.58 s and 0.61 s are the MDC95 required in four conditions. Conclusion: Absolute variability and relative reliability of the timed standing balance test in children with DS have been established.