Introduction <p>Efficiently meeting recruitment targets is foundational to clinical trial success. Past reviews on improving recruitment efficiency have highlighted only a few evidence-supported strategies; some of which may be context-specific, infeasible, or unsustainable. Re-framing research participation as a behaviour subject to the same forces as other human behaviours allows us to consider whether knowledge about behaviour change in other contexts can be applied to trial recruitment, potentially leading to more efficient theory-informed strategies. This study assessed randomised evaluations of recruitment interventions regarding (1) whether and how they reported using theory and (2) the extent behaviour change techniques (BCTs) were identifiable within recruitment methods and interventions.</p> Methods <p>We examined reports of randomised evaluations of recruitment interventions from a Cochrane review of trials evaluating strategies to improve recruitment, and the online resource for research in clinical trials database. To be eligible, studies had to include recruitment or willingness-to-participate outcomes. First, we assessed how and to what extent authors reported using theories, models, or frameworks in any part of their trial. Second, we extracted use of BCTs from study recruitment methods guided by the BCT taxonomy.</p> Results <p>We included 122 recruitment intervention studies. Few (<i>n</i> = 23, 19%) explicitly reported theory, model, or framework use; most often, theory was used to inform the intervention design (<i>n</i> = 15, 12%) or justification (<i>n</i> = 14, 11%). The most frequently cited theories included the theory of planned behaviour (<i>n</i> = 7, 6%) and prospect theory (<i>n</i> = 3, 3%). Studies contained anywhere from one identifiable BCT (<i>n</i> = 43, 35%) up to seven (<i>n</i> = 2, 2%); these typically included providing information about health consequences (e.g. side effects; <i>n</i> = 25, 21%), information about social and environmental consequences (e.g. helping society; <i>n</i> = 30, 25%), and prompts/cues (e.g. reminders; <i>n</i> = 25, 21%). Many studies did not report any codable BCTs (<i>n</i> = 35, 29%).</p> Conclusions <p>Studies evaluating recruitment interventions often fail to report any consideration of theories, models, or frameworks, and many well-understood behaviour change techniques are generally not reported. Future research that frames clinical trial participation as one or more behaviours may broaden the range of empirically based strategies available to support participation and lead to more productive evaluations of theory-guided, elemental, and empirically supported recruitment strategies.</p>