An 88-year-old woman was diagnosed with multiple myeloma received third-line chemotherapy, including DBd (daratumumab [DARA], bortezomib, and dexamethasone [Dex]), and the myeloma was in remission. Sulfamethoxazole/trimethoprim (ST) prophylaxis was discontinued because the dose of Dex was reduced to 20 mg every 4 weeks after 21 cycles of DBd. After 28 cycles of DBd, altered consciousness with fever ensued, and she was referred to the emergency department where Listeria monocytogenes (LM) meningitis was diagnosed. CD38 inactivation is associated with increased LM susceptibility. In patients on Dara-based chemotherapy, antibiotic prophylaxis should be considered using ST, which has activity against Listeria.