Drug interactions occur frequently with triazole antifungal agents because of their properties as inhibitors of 1 or more phase 1 (cytochrome P450) biotransformation enzymes and, possibly, as inhibitors or substrates of a phase 2 biotransformation enzyme or transporter protein. Multimorbid patients, including those with hematologic malignancies or other cancers, hematopoietic stem cell or organ transplant recipients, patients infected with the human immunodeficiency virus, and those in the intensive care unit, are at increased risk for drug interactions because they typically require several concomitant medications. They may also be extremely vulnerable to the clinical signs and symptoms of drug interactions. This review describes clinically significant drug interactions most frequently seen in multimorbid patients who receive systemic therapy with triazole antifungals for the prophylaxis or treatment of invasive fungal infections; including interactions with corticosteroids, immunosuppressants, anti-infective drugs, benzodiazepines, opioid analgesics, statins, anticoagulants, anticonvulsants, and drugs affecting gastric pH. The review also describes recommendations concerning contraindications and dose-modification strategies. The azoles differ markedly in their pharmacokinetic and antifungal properties, safety and tolerability, and drug-interaction profiles. Many drug interactions can be prevented if clinicians are thoroughly familiar with the pharmacokinetic profiles of different azoles, follow contraindications and dose-modification recommendations, and switch azoles when possible to achieve the best combination of clinical efficacy and safety. Therapeutic drug monitoring can help optimize treatment and prevent underdosing or overdosing of drugs. Education of patients and their families about signs and symptoms of possible drug interactions is also beneficial.