Background: Survivors of childhood cancer experience an increasing incidence of late sequelae with age, with the effect on health likely compounded by limited physical activity and low cardiorespiratory fitness (CRF). This study aimed to determine survivors’ physical activity levels and to objectively measure CRF, compared with controls. Methods:Stage 1: We collected physical activity data from parents of survivors aged 7-18 years, ≥5 years after diagnosis, from 11 Australian and New Zealand hospitals and from age-matched controls (International Physical Activity Questionnaire). We compared moderate-vigorous physical activity with American Cancer Society guidelines (≥300 min/week). Stage 2: We assessed CRF in survivors aged 8-18 years, ≥1 year after treatment completion, by cardiopulmonary exercise test (Bruce Protocol), 6-minute walk test (6MWT), and self-reported fitness (International Fitness Scale). Results:Stage 1: 192 parents of survivors (age = 12.9±2.3 years) and 111 parents of control children (age = 12.3±2.7 years) participated. Parents reported survivors participated in more physical activity than controls (248.4±217.6 vs 184.8±213.6 min/week, p = 0.036), with 31% of survivors meeting physical activity guidelines, compared with 22.7% of controls (p = 0.011). Stage 2: 31 survivors (age = 13.0±3.5 years) and 10 controls (age = 10.6±1.1 years) completed CRF assessments. Survivors appear to have similar CRF compared with controls in terms of VO2max (41.1 vs 46.8ml/kg/min, p = 0.09; 40^th vs 60^th percentile, p = 0.11) and 6MWT distance percentile (69^th vs 78^th percentile, p = 0.30). Among survivors, a weak linear relationship existed between self-perceived CRF and VO2max percentile (r²= 0.20, p = 0.017). Conclusions: Only one-third of childhood cancer survivors met physical activity guidelines, whilst survivors and controls reported similar fitness. Considering the late-effects risks during aging in survivors, regularly assessing physical activity and CRF provides clinicians with vital information to monitor survivors. Although survivors accurately perceived their CRF, the weak relationship reinforces the need for accurate assessment to provide insight into cardiovascular risk.