Background. Acute Lymphoblastic Leukemia (ALL) is a hematolymphoid neoplasm with multiple complications and variable prognosis, which depends on several factors, one of them related to chemotherapeutic treatment. Objective. To describe the complications developed in patients diagnosed with ALL and who received chemotherapy treatment in Hospital San Rafael. Materials and methods. A retrospective analysis of clinical, paraclinical and demographic variables taken from clinical records of adult patients diagnosed with ALL admitted to hospital between 2016 and 2017. Results. A hundred and sixteen patients had hematological malignancies, 24 had ALL. Most of them had B-cell precursor ALL (79.2 %), 86.4 % were in the chemotherapy induction phase, 87.5 % developed febrile neutropenia, 37.5 % had tumor lysis syndrome, 58.3 % developed infectious complications, and 45.8 % died. Discussion. This is the first study known to date describing the complications in patients with ALL at Hospital San Rafael in Colombia. One of the major findings was the high frequency of febrile neutropenia episodes and infectious complications mainly associated with unfavorable outcomes, such as multiple organ failure and death. Therefore, clinicians should always have these complications in mind when a patient with hematological malignancies is receiving or is about to start a chemotherapeutic regimen. Conclusions. Bloodborne and respiratory tract infections were the most common sources of infection by Staphylococcus epidermidis and Klebsiella pneumoniae as causative agents. Likewise, the most frequent complication was febrile neutropenia. The first cause of death were infections complicated by sepsis; however, only one-third of the patients had a microbial isolation.