Abstract Background Antibiotic prescribing for acute self-limiting respiratory tract infections (ARTIs) in Australia is higher than international benchmarks. Antibiotics have little or no efficacy in these conditions, and unnecessary use contributes to antibiotic resistance. Delayed prescribing has been shown to reduce antibiotic use. GP registrars are at a career-stage when long-term prescribing patterns are being established. Aim To explore experiences, perceptions and attitudes of GP registrars and supervisors to delayed antibiotic prescribing for ARTIs. Design and setting A qualitative study of Australian GP registrars and supervisors using a thematic analysis approach. Method GP registrars and supervisors were recruited across three Australian states/territories, using maximum variation sampling. Telephone interviews explored participants’ experience and perceptions of delayed prescribing of antibiotics in ARTIs. Data collection and analysis were concurrent and iterative. Results A total of 12 registrars and 10 supervisors were interviewed. Key themes included the use of delayed prescribing as a safety-net in cases of diagnostic uncertainty or when clinical review was logistically difficult. Delayed prescribing was viewed as a method of educating and empowering patients, and building trust and the doctor–patient relationship. Conversely, it was also seen as a loss of control over management decisions. Supervisors, more so than registrars, appreciated the psychosocial complexity of ARTI consultations and the importance of delayed antibiotic prescribing in this context. Conclusion Better awareness and understanding by GP registrars of the evidence for delayed antibiotic prescription may be a means of reducing antibiotic prescribing. Understanding both registrar and supervisor usage, uncertainties and attitudes should inform educational approaches on this topic.