Adverse drug reactions (ADRs) are one of the major causes of mortality. One of the major causes of ADR is drug–drug interactions. The purpose of this study was to evaluate the prevalence and characteristics of ADRs caused by the drug interactions in the nephrology departments. Methods: This cross-sectional prospective study was carried out in the nephrology department on 117 patients who received at least two medicines. Drug interactions were determined, and the patients were evaluated for the presence of a drug complication. Findings: A total of fifty ADRs were observed in 39 patients, whereas 26% of total ADRs (13 drug complications) were due to drug interactions. About 69% and 31% of complications were classified in terms of severity, in the category of “severe” and “moderate” complications, respectively. Warfarin had the highest contribution to major interactions (33.33%). Conclusion: ADRs, which specially occurred due to drug interactions, are particularly important for patients taking multiple medications (e.g., patient with renal insufficiency). Therefore, special attention should be paid to preventing and reducing ADRs in these patients' population.