Abstract Background Longer duration from symptom onset is associated with increased risk of perforation in appendicitis. In previous studies, in-hospital delay to surgery has had conflicting effects on perforation rates. Although preoperative antibiotics have been shown to reduce postoperative infections, there are no data showing that administration of antibiotics while waiting for surgery has any benefits. The aims of this study are to evaluate the role of both in-hospital delay to surgery and antibiotic treatment while waiting for surgery on the rate of appendiceal perforation. Methods This prospective, open-label, randomized, controlled non-inferiority trial compares the in-hospital delay to surgery of less than 8 hours versus less than 24 hours in adult patients with predicted uncomplicated acute appendicitis. Additionally, participants are randomized either to receive or not to receive antibiotics while waiting for surgery. The primary study endpoint is the rate of perforated appendicitis discovered during appendicectomy. The aim is to randomize 1800 patients, that is estimated to give a power of 90 per cent (χ2) for the non-inferiority margin of 5 percentage points for both layers (urgency and preoperative antibiotic). Secondary endpoints include length of hospital stay, 30-day complications graded using Clavien–Dindo classification, preoperative pain, conversion rate, histopathological diagnosis and Sunshine Appendicitis Grading System classification. Discussion There are no previous randomized controlled studies for either in-hospital delay or preoperative antibiotic treatment. The trial will yield new level 1 evidence. EU Clinical Trials Register, EudraCT Number: 2019–002348-26; registration number: NCT04378868 (http://www.clinicaltrials.gov)