There is an increased risk of potential drug–drug interactions (pDDIs) in critically ill patients based on the number of drugs received. The occurrence of pDDIs and clinical significance is not well described. The aim was to provide insight into important clinical issues and offer guidance on drug–drug interaction (DDI) surveillance through the performance of a systematic review. Five targeted objectives were developed, a priori, which guided study selection and data abstraction. Two independent reviewers extracted the definition, frequency, type, and clinical significance of pDDIs. A meta-analysis was performed to evaluate the proportion of patients exposed to a pDDI. Three data sources (PubMed, Embase, and Scopus) were utilized for the search to include studies that evaluated pDDIs in adult critically ill patients. Included studies in the systematic review and meta-analysis were required to be full text. A total of 39 studies met inclusion criteria. Definitions of pDDIs were diverse. Frequency of pDDIs varied by study, but was most commonly between one and five pDDIs per patient. Fifty-eight percent of patients were exposed to at least one pDDI during their intensive care unit admission. Types of pDDIs identified were numerous, with aspirin being the most common drug involved. As expected, not all pDDIs were clinically significant. Clinical significance was determined by varied definitions and sources. Improving the understanding of clinically significant pDDIs and alerts that clinicians encounter may guide better development of surveillance through clinical decision support and decrease alert fatigue.