Background Survivors of paediatric brain cancer and/or cranial radiotherapy (CRT) are at an increased risk of developing serious comorbidities. Established risk factors for chronic disease include central obesity, endothelial abnormalities and diminished fitness. Objectives Here we characterised anthropometry, body composition, bone mineral density (BMD), heart rate (HR), blood pressure (BP), endothelial function, muscular strength and endurance and aerobic fitness in adolescent and young adult (AYA) survivors. Methods Twenty survivors (10 male, 10 female; 20 ± 2 years) were compared with 19 matched controls. Muscular strength was assessed using three repetition maximum tests, while muscular endurance was determined as number of repetitions performed per minute. Peak oxygen uptake (VO2 peak) was assessed on a treadmill using a modified chronotropic protocol. Anthropometric measurements, HR and BP were taken using standard clinical protocols, while body composition and BMD were determined using dual X-ray absorptiometry (DXA). Endothelial function was measured using the flow mediated dilation technique. Results Survivors demonstrated deficits in muscular strength (latissimus dorsi pull-down, p = 0.020; bicep curl, p = 0.009), muscular endurance (squats, p = 0.012; sit-ups, p = 0.030; push-ups, p = 0.013), minute ventilation at peak exericse (p = 0.002) and VO2peak (L/min, p = 0.002; mL/kg/min, p = 0.008; mL/kg LBM/min, p = 0.010). Additionally, survivors had greater waist-to-hip ratios (p = 0.032), resting HR (p = 0.048) and higher percentage of total body (p = 0.017), central (p = 0.009) and peripheral (p = 0.032) fat. Lean body mass (p = 0.004) and BMD (p = 0.005) were lower in the survivor group. Conclusion AYA survivors of paediatric brain cancer and/or CRT exhibit altered body composition, increased resting HR and reduced BMD, muscular strength, muscular endurance and cardiorespiratory fitness compared to controls.