The Tower Test in the Delis-Kaplan Executive Function System (D-KEFS) is a widely-used assessment of executive function in young people. It is similar to other Towers of Hanoi type tasks, for which doubts regarding the reliability of the test have been previously raised. Here, we present data on the internal consistency, unidimensionality, and test–retest reliability of the D-KEFS Towers Test based on an Ecuadorian sample of 264 children and adolescents. In general, the Tower Test appeared to have poor reliability. This may be caused by the combination of very simple and more difficult trials within the same assessment. Nevertheless, one measure, the Time-Per-Move Ratio, appeared to be sufficiently reliable for clinical or research use, and neuropsychological studies have suggested that the Time-Per-Move Ratio may also be the performance measure most sensitive to neurological impairment.