The study investigated the stability of executive functioning (EF) measures in children and adolescents aged 8–17 years with unilateral cerebral palsy (CP). Here 44 participants with unilateral CP (mean age = 11 years, 11 months; Manual Abilities Classification Scale Level I = 6 and Level II = 37; Gross Motor Function Classification Scale Level I = 22 and Level II = 22) were randomized into the wait-list control group of a large randomized controlled trial. Participants had baseline testing with Wechsler Intelligence Scale for Children – Fourth Edition Short Form (WISC-IV-SF) and Delis-Kaplan Executive Function System (D-KEFS) subtests. Parents completed the Behavior Rating Inventory of Executive Functioning (BRIEF). Participants were re-assessed 20 ±2 weeks later with a shortened test battery including the D-KEFS subtests; Digit Span, Coding and Symbol Search (WISC-IV); and BRIEF. Pearson’s test–retest reliabilities and Reliable change scores were calculated. Results indicated excellent to fair test–retest reliabilities (r = 0.91–0.74) for all measures except Digit Span Backwards (r = 0.62), Inhibition (r = 0.69), and Initiate (r = 0.68). Reliable change scores applying 90% confidence intervals for estimating reliable change while accounting for practice effects were provided for all measures. The data support the stability of EF measures in this population.