Background Medical errors account for up to 440,000 deaths annually, and cognitive errors outpace knowledge deficits as causes of error. Cognitive biases are predispositions to respond in predictable ways, and they don’t always result in error. We conducted a scoping review exploring which biases are most prevalent in Internal Medicine (IM), if and how they influence patient outcomes, and what, if any, debiasing strategies are effective. Content We searched PubMed, OVID, ERIC, SCOPUS, PsychINFO, and CINAHL. Search terms included variations of “bias”, “clinical reasoning”, and IM subspecialties. Inclusion criteria were: discussing bias, clinical reasoning, and physician participants. Summary Fifteen of 334 identified papers were included. Two papers looked beyond general IM: one each in Infectious Diseases and Critical Care. Nine papers distinguished bias from error, whereas four referenced error in their definition of bias. The most commonly studied outcomes were diagnosis, treatment, and physician impact in 47 % (7), 33 % (5), and 27 % (4) of studies, respectively. Three studies directly assessed patient outcomes. The most commonly cited biases were availability bias (60 %, 9), confirmation bias (40 %, 6), anchoring (40 %, 6), and premature closure (33 %, 5). Proposed contributing features were years of practice, stressors, and practice setting. One study found that years of practice negatively correlated with susceptibility to bias. Ten studies discussed debiasing; all reported weak or equivocal efficacy. Outlook We found 41 biases in IM and 22 features that may predispose physicians to bias. We found little evidence directly linking biases to error, which could account for the weak evidence of bias countermeasure efficacy. Future study clearly delineating bias from error and directly assessing clinical outcomes would be insightful.