Therapeutic options for infections caused by Carbapenem‐resistant Enterobacterales (CRE) are restricted and include polymyxins‐centred schemes. Evaluation of in vitro susceptibility is difficult and time consuming. Agar‐based methodologies are an alternative to broth microdilution (BMD) and we aimed to evaluate the accuracy of those methods among Enterobacterales. A total of 137 non‐duplicated CRE were subjected to polymyxin B BMD, agar screening test (Mueller Hinton plates containing 3 µg ml−1 of polymyxin B) and agar dilution (antibiotic serially diluted 0·25–64 µg ml−1). CRE of 42·3% were resistant to polymyxin B (MICs range: 0·25–>64 µg ml−1) and 16·8% presented borderline MICs. Sensitivity, specificity, PPV and NPV were 86·2, 98·7, 98 and 90·7% for screening test and 86·2, 97·5, 96·1 and 90·6% for agar dilution. ME was 0·73 and 1·5% for screening and agar dilution respectively; VME was 5·8% for both techniques. In general, agar‐based methods had a good performance. As far as we know, this is the first study to propose an agar screening test using polymyxin B instead of colistin.