Abstract Background In ± 10% of all Crohn’s disease (CD) patients a perianal abscess (PAA) or fistula (PAF) is the manifesting symptom. The delay in diagnosis of CD, from fistula or abscess onset, is very long and associated with worse outcomes. The aim of this Delphi study was to reach consensus on a clinical decision tool to help select patients with raised suspicion of CD in PAA/PAF patients, to identify underlying CD earlier and reduce the diagnostic delay. Methods A panel of international experts in the field of proctology and/or Inflammatory Bowel Disease (IBD), consisting of surgeons, gastroenterologists and radiologists were invited to participate in the PREFAB part of this Delphi study. The first round was an electronic survey and the second round a virtual consensus meeting. In the first round, participants were asked to anonymously provide their opinion probing 1) the relevance and use of clinical characteristics (“Red Flags”) suggestive of underlying CD, 2) the use of faecal calprotectin (FCP) as an adjunct for screening for CD and 3) on the diagnostic work-up for IBD in PAA/PAF patients with raised clinical suspicion. In the second round, statements were paired/revised based on the feedback from the first round and presented in a final set of statements. Consensus was predefined as ≥70% agreement. Results A total of 30 experts participated in the first round and 25 in the second round (83.3%). Final consensus was reached for 29% of all statements in the first Delphi round and, after adjustments/merging, for all 11 statements (100%) in the second round. Ninety-seven percent of participants agreed that shortening of the delay in diagnosis by using a clinical decision tool could improve outcomes in patients with perianal disease as a first symptom. Consensus was reached on the red flags to be included in the clinical decision tool, on screening of all patients with any perianal fistula (regardless of the complexity, biological behaviour and co-existent perianal symptoms) to identify CD in an early (sub)clinical phase, on referral criteria and on the diagnostic workup and follow up of patients with raised suspicion. Conclusion A clinical decision tool for early identification of CD in patients with PAA/PAF as a first symptom could shorten delay in diagnosis and improve outcomes. Global consensus for this tool, including a practical and relevant algorithm for finding or excluding CD in patients with PAA/PAF as a manifesting sign, was reached within two rounds. This clinical decision tool will be validated in 2024 in a large, prospective multicenter study.