Objective To develop a theory and evidence-based web intervention to reduce psychological barriers towards insulin therapy among adults with non-insulin-treated type 2 diabetes (T2D). Methods Salient psychological barriers towards insulin were identified from the literature and classified using the Theoretical Domains Framework (TDF). Relevant TDF domains were mapped to evidence-based behaviour change techniques (BCTs), which informed the content for each barrier. Acceptability was explored using cognitive debriefing interviews (n=6 adults with T2D). Results 'Is Insulin Right for Me' addresses eight barriers, phrased as common questions: Does insulin mean my diabetes is more serious? Do insulin injections cause complications? Is it my fault I need to inject insulin? Will I gain weight? Will injecting hurt? What about hypos? Will injecting insulin be a burden? What will others think of me? BCTs, including persuasive communication and modelling/demonstration, were delivered using appropriate methods (eg, demonstration of the injection process). Participant suggestions for improvement included clear and direct messages, normalising insulin and avoiding confronting images. Conclusions 'Is Insulin Right for Me' is the first theory and evidence-based, web intervention designed to reduce psychological barriers towards insulin therapy for adults with T2D. Evaluation is needed to determine its impact on negative appraisals and receptiveness towards insulin.