Assessment of lower respiratory tract infection in children with cancer or post-hematopoietic stem cell transplant requires a sample of the lower airways, which can be accomplished through bronchoalveolar lavage (BAL). The benefits and hazards of BAL might be difficult for clinicians to weigh. The purpose of this research was to characterize the diagnostic and clinical value of BAL in this patient group. BAL in children post-hematopoietic stem cell transplant or for children with cancer: this was a retrospective study of 1 center. Demographic information, BAL procedure and outcomes, and antibiotic use were all culled from the data. Both univariate and multivariate analyses were performed to determine which factors were substantially linked with diagnostic yield, diagnostic impact (confirmation or exclusion of infection), and clinical impact (any change in antimicrobial or nonantimicrobial therapy). A total of 73 BAL episodes were compiled. Pathogens were detected on BAL in 26 cases (35.6%), 49 (67%) of BAL events were significant in some way to the diagnosis, and 15 (21%) were clinically significant. Multivariate analysis indicated that flexible bronchoscopy (odds ratio 6.10; 95% CI: 1.90-24.0) and late BAL (>72 hours) were more likely to have a diagnostic influence than early BAL (odds ratio 3.27; 95% CI: 1.03–10.86).  No correlations regarding clinical relevance were discovered. Approximately 1/3rd of BAL incidents resulted in the identification of a pathogen, 2/3rd had an impact on diagnosis, and nearly a quarter of episodes affected antibiotic prescribing. Flexible bronchoscopy is 6 times more probable, and late BAL is 3 times more likely to have a diagnostic impact than early BAL.