Background With improved survival rates in pediatric oncology, the detection of adverse side- and late-effects is gaining increased interest. This cross-sectional study investigated walking abilities and ankle dorsiflexion function in children with cancer. Patients Study participants included 16 children with various cancers (4–20 years, patient group) after completion of the intense treatment and 16 age- and gender-matched healthy peers (comparison group). Method Walking speed (10-meter-walking-test, treadmill test assessing preferred transition speed), walking capacity (2-minute-walk-test), walking balance (Timed-Up-And-Go-Test), active/passive ankle dorsiflexion range of motion (ROM) (goniometer) and ankle dorsiflexion strength (hand-held dynamometer) were comprehensively assessed. Results Significant lower values in the patient group were found for walking capacity, maximum walking speed, ankle dorsiflexion ROM and strength. No significant differences between the groups were found for preferred walking speed and walking balance. Discussion Limited walking abilities and ankle dorsiflexion dysfunctions are prominent in children with cancer; having the potential to impact children’s community mobility and physical activity. Conclusions To provide holistic care, the development of specific supportive strategies such as exercise interventions and its translation into clinical practice needs to be accelerated.