The trajectory of hematopoietic stem cell transplantation (HSCT) is often accompanied by physically disabling complications that impair physical performance of pediatric patients. However, knowledge about when impairments in physical performance arise and the factors contributing to these impairments is limited. Therefore, we conducted a retrospective analysis of physical performance 100 days post-HSCT in patients aged 3-18 years. Additionally, we aim to elucidate the relationship between pre-and post-HSCT physical performance and to unravel the impact of intensive HSCT procedures on post-HSCT physical performance. To explore associations between physical performance outcomes post-HSCT and covariates, linear regression models were estimated. Seventyseven patients were included with a median age of 11.8 years (interquartile range: 5.9, 14.8). Patients had lower hip flexion muscle strength and appendicular skeletal muscle mass and a slower rising from the floor time 100 days post-HSCT compared to average values of the normal population. Pre-HSCT physical performance was positively associated with physical performance post-HSCT, independent of age, the cumulative glucocorticoids dosage administered and the total duration of hospitalization during the HSCT trajectory. This explorative study highlights the potential role of prehabilitation in enhancing physical performance of pediatric HSCT patients.