Background: Daratumumab is an anti-CD38 monoclonal antibody indicated for the treatment of multiple myeloma. Infusion-related reactions (IRRs) are among the most common adverse events associated with daratumumab. IRRs are most common with the first infusion of daratumumab. Recommended premedications to be given prior to the daratumumab dose include acetaminophen, diphenhydramine, and a corticosteroid. There is emerging data to suggest that the addition of montelukast to this premedication regimen can lower the incidence of daratumumab-related IRRs.Patients And Methods: This was a single-center, retrospective chart review conducted at a large, multistate health system with several different hematology/oncology practice sites. Eligible patients included those with a primary diagnosis of a plasma cell disorder who received at least 1 dose of daratumumab. The primary outcome was the incidence of IRRs with the first daratumumab infusion.Results: A total of 141 patients receiving daratumumab-based therapy were included in this study. All patients received acetaminophen, diphenhydramine, and a corticosteroid as premedications prior to the first infusion of daratumumab. Overall, 46 (33%) patients experienced an IRR with the first infusion of daratumumab. The incidence of IRR was lower in patients that received montelukast as a premedication compared with those that did not (montelukast, n = 25 [27%]; no montelukast, n = 21 [45%]; P = .0371). Patients in each arm experienced similar rates of overall, composite pulmonary, gastrointestinal, and systemic IRR manifestations.Conclusion: The use of montelukast prior to the first daratumumab infusion led to a reduction in the incidence of IRRs in our experience.