IMPORTANCE: Implementation of new cancer treatment strategies as recommended by evidence-based guidelines is often slow and suboptimal. OBJECTIVE: To improve the implementation of guideline-based best practices in the Netherlands in pancreatic cancer care and assess the impact on survival. DESIGN, SETTING, AND PARTICIPANTS: This multicenter, stepped-wedge cluster randomized trial compared enhanced implementation of best practices with usual care in consecutive patients with all stages of pancreatic cancer. It took place from May 22, 2018 through July 9, 2020. Data were analyzed from April 1, 2022, through February 1, 2023. It included all patients in the Netherlands with pathologically or clinically diagnosed pancreatic ductal adenocarcinoma. This study reports 1-year follow-up (or shorter in case of deceased patients). INTERVENTION: The 5 best practices included optimal use of perioperative chemotherapy, palliative chemotherapy, pancreatic enzyme replacement therapy (PERT), referral to a dietician, and use of metal stents in patients with biliary obstruction. A 6-week implementation period was completed, in a randomized order, in all 17 Dutch networks for pancreatic cancer care. MAIN OUTCOMES AND MEASURES: The primary outcome was 1-year survival. Secondary outcomes included adherence to best practices and quality of life (European Organisation for Research and Treatment of Cancer [EORTC] global health score). RESULTS: Overall, 5887 patients with pancreatic cancer (median age, 72.0 [IQR, 64.0-79.0] years; 50% female) were enrolled, 2641 before and 2939 after implementation of best practices (307 during wash-in period). One-year survival was 24% vs 23% (hazard ratio, 0.98, 95% CI, 0.88-1.08). There was no difference in the use of neoadjuvant chemotherapy (11% vs 11%), adjuvant chemotherapy (48% vs 51%), and referral to a dietician (59% vs 63%), while the use of palliative chemotherapy (24% vs 30%; odds ratio [OR], 1.38; 95% CI, 1.10-1.74), PERT (34% vs 45%; OR, 1.64; 95% CI, 1.28-2.11), and metal biliary stents ...