Objective Since pulmonary complications are a major cause of mortality in patients with hematologic diseases, their rapid detection and treatment are essential. Bronchoalveolar lavage (BAL) is widely performed to diagnose pulmonary infiltrates not evident with non-invasive investigations; however, reports on its clinical benefits for patients with hematologic diseases are limited. The aim of our study was to investigate the utility of diagnostic bronchoscopy with BAL for those patients.Methods We retrospectively reviewed the clinical records of 37 consecutive BAL procedures in 33 adult patients with hematological diseases and pulmonary infiltrates with at least 6 months of follow-up between August 2013 and September 2017 (total 747 BAL procedures). The BAL results, ensuing treatment modifications, treatment outcomes, survival times, and adverse events were evaluated.Results Microbiological findings were detected in 11 (29.7%), even though wide-spectrum antibiotics and antifungal drugs had been empirically administered to most patients (> 70%) prior to the bronchoscopy procedure. Overall, 25 of the 37 BAL procedures (67.6%) had some impact on the diagnosis of pulmonary diseases. Patients without specific diagnostic findings from BAL had a significantly poorer survival than those with diagnostic findings via BAL (30-day survival: 33.3% vs. 92.0%; 180-day survival: 8.3% vs. 64.0%). Four patients (12.1%) experienced complications associated with bronchoscopy; there were no procedure-related deaths.Conclusion BAL seems still important for diagnosing pulmonary infiltrates and/or excluding some of the important respiratory tract pathogens in patients with hematological diseases; furthermore, negative specific diagnostic findings from BAL may be associated with poor prognoses.