Background Diagnostic errors remain a significant challenge in healthcare, with cognitive biases, particularly availability bias, playing a critical role. While previous studies focused on controlled experimental settings, this study investigates the real-world impact of clinical practice on susceptibility to the availability bias. Methods Using a cross-sectional survey-based design, we assessed 1015 physicians’ responses to clinical cases in the form of vignettes after they attended (vs did not attend) a patient with the disease of interest in the last 7 days. Physicians’ specialisations and years of experience were also measured, allowing us to assess the presence of the availability bias and the interacting roles of clinical experience and expertise. Results Recent clinical encounters with a disease increased the likelihood of erroneously diagnosing it (availability bias, b=0.165, SE=0.070, p=0.018). Among specialists, having 10 or more years of experience decreased the likelihood of an erroneous diagnostic (b=–0.361, SE=0.180, p=0.046). The results indicated distinct effects of experience and specialisation on susceptibility to the availability bias. Conclusions Availability bias can be triggered by real clinical encounters and is modulated by the interplay between experience and domain-specific expertise. Structured, feedback-rich exposure—rather than mere experience—appears crucial to mitigating cognitive biases. These findings reinforce the role of knowledge—both formal and experiential—in mitigating the bias, and the importance of developing true expertise. Data are available upon reasonable request.