Background: Mannitol has been used in the past for the prevention of cisplatin-induced nephrotoxicity. Studies on its efficacy have conflicting results. An educational newsletter was designed for local oncologists on the conflicting data of mannitol use in preventing cisplatin-induced nephrotoxicity. Purpose: The purpose of this study was to determine whether a pharmacist-created newsletter intervention led to changes in the mannitol prescribing practices of local oncologists. Methods: A newsletter describing the paucity of evidence to support mannitol use to prevent cisplatin-induced nephrotoxicity was distributed via e-mail to local oncologists in October 2010. Mannitol prescribing rates were retrospectively evaluated before and after newsletter distribution. The Mann-Whitney U test was used to compare nonparametric continuous data. The chi-square test was used for nominal data. Descriptive statistics were performed for baseline demographics, and odds ratios were calculated for possible risk factors for acute kidney injury (AKI). The primary endpoint was a change in mean mannitol dose before and after the newsletter intervention. The secondary endpoint was the difference in the rate of AKI before and after the intervention. Data were collected for 67 patients with various malignancies. Results: There was a difference in the average mannitol dose before and after newsletter intervention (P = .02). The rates of AKI before and after newsletter were similar. Conclusion: A pharmacist-led newsletter intervention was associated with significantly decreased rates of mannitol usage after intervention.