BACKGROUND: The aim of this study was to determine the absolute and relative reliability of the Ruler Drop Test (RDT) for assessing dual-task, choice, and discrimination reaction time. In addition, the construct validity of the RDT is examined in comparison to the Deary-Liewald reaction time (DLRT). METHODS: Tests were administered by the same evaluator, one week apart. Intraclass Correlation Coefficient (ICC3.1) was used to measure relative reliability, and the standard error of measurement (SEM) and minimal detectable change (MDC95) were used to measure absolute reliability. Spearman correlation test was used to measure construct validity. RESULTS: The results showed that the relative reliability was good for the choice ruler drop (ICC = 0.81), moderate for the dual-task ruler drop test (ICC = 0.70) and discrimination ruler drop test (ICC = 0.72), and good for simple ruler drop test. However, the simple ruler drop test had poor reliability (ICC = 0.57). The RDT shows construct validity compared to the DLRT. CONCLUSION: We conclude that the RDT is a suitable instrument for measuring dual-task, choice and discrimination reaction time. Future studies should explore the reliability of these measures in other populations.