The del Nido cardioplegia solution has been used extensively in congenital heart surgery for more than 20 years and more recently for adults. This randomized controlled trial examined whether expanding this technique to adult cardiac surgery confers benefits in surgical workflow and clinical outcome compared with blood-based cardioplegia. Adult first-time coronary artery bypass grafting (CABG), valve, or CABG/valve surgery patients requiring cardiopulmonary bypass (CPB) were randomized to del Nido cardioplegia (n = 48) or whole blood cardioplegia (n = 41). Primary outcomes assessed myocardial preservation. Troponin I was measured at baseline, 2 hours after CPB termination, 12 and 24 hours after cardiovascular intensive care unit admission. Alpha was set at P < .001. Preoperative characteristics were similar between groups, including age, Society of Thoracic Surgeons risk score, CABG, and valve procedures. There was no significant difference on CPB time (97 vs 103 minutes; P = .288) or crossclamp time (70 vs 83 minutes; P = .018). The del Nido group showed higher return to spontaneous rhythm (97.7% vs 81.6%; P = .023) and fewer patients required inotropic support (65.1% vs 84.2%; P = .050), but did not reach statistical significance. Incidence of Society of Thoracic Surgeons-defined morbidity was low, with no strokes, myocardial infarctions, renal failure, or operative deaths. For del Nido group patients, troponin levels did not increase as much as for control patients (P = .040), but statistical significance was not reached. Evidence from this study suggests del Nido cardioplegia use in routine adult cases may be safe, result in comparable clinical outcomes, and streamline surgical workflow. The trend for troponin should be investigated further because it may suggest superior myocardial protection with the del Nido solution.