Objective:To establish the optimal time to start oral refeeding in mild and moderate acute pancreatitis (AP) to reduce hospital length-of-stay (LOS) and complications.Summary Background Data:Oral diet is essential in mild and moderate AP. The greatest benefits are obtained if refeeding starts early; however, the definition of “early” remains controversial.Methods:This multicenter, randomized, controlled trial (NCT03829085) included patients with a diagnosis of mild or moderate AP admitted consecutively to 4 hospitals from 2017 to 2019. Patients were randomized into 2 treatment groups: immediate oral refeeding (IORF) and conventional oral refeeding (CORF). The IORF group (low-fat-solid diet initiated immediately after hospital admission) was compared to CORF group (progressive oral diet was restarted when clinical and laboratory parameters had improved) in terms of LOS (primary endpoint), pain relapse, diet intolerance, complications, and, hospital costs.Results:One hundred and thirty one patients were included for randomization. The mean LOS for the IORF and CORF groups was 3.4 (SD ± 1.7) and 8.8 (SD ± 7.9) days, respectively (P < 0.001). In the CORF group alone, pain relapse rate was 16%. There were fewer complications (8% vs 26%) and health costs were twice as low, with a savings of 1325.7€/patient in the IORF than CORF group.Conclusions:IORF is safe and feasible in mild and moderate AP, resulting in significantly shorter LOS and cost savings, without causing adverse effects or complications.