Objective:The aim of the study was to document the frequency, severity, evolution, and impact of adverse events (AE) on chemotherapy and the clinical evolution of patients with hematologic malignancies. Material and Methods: A prospective study was carried out at a hematology reference center in Northeastern Mexico over 1 year. All patients with malignant disease developing adverse chemotherapy events were included in the study. AEs were classified according to Common Terminology Criteria for AEs v5.0. Results: One-hundred and seventy-four patients attended the hematology clinic for outpatient chemotherapy. Acute lymphoblastic leukemia accounted for 51.7%, non-Hodgkin's lymphoma 25.9%, acute myeloid leukemia 9.8%, multiple myeloma 6.3%, Hodgkin's lymphoma 5.7%, and chronic myeloid leukemia 0.6% of the cases. A total of 191 AEs, including 79 hospital admissions, were registered in 58 (33.3%) patients. About 62.3% of the cases were Grade 3, in 43.9% of the events complete resolution was achieved, whereas the chemotherapy regimen had to be suspended in 13.6% of the cases. Febrile neutropenia was the main AE, documented in 77.6%; four (6.9%) patients died as a direct consequence of this complication. Thrombocytopenia occurred in 65.5% and anemia in 55.2%, with no deaths. Conclusions: AEs secondary to chemotherapeutic drugs used in the treatment of hematological malignancies constitute an important cause of morbidity and occasional mortality and should be closely monitored and documented.