ObjectiveThe rather broad definition of medical trauma within DSM‐IV has contributed to long‐lasting debates on the applicability of Posttraumatic Stress Disorder (PTSD) in oncological patients and its differentiation from Adjustment Disorder (AjD) which results from non‐traumatic critical life events. The DSM‐5 criteria have introduced a narrower definition of medical traumatization. However, studies on updated prevalence rates in cancer patients are missing.MethodsWithin a cross‐sectional study, we assessed hematological cancer survivors using the Structured Clinical Interview for DSM‐5. We investigated (i) the frequency and type of cancer‐related stressors, (ii) the proportion of stressors qualifying as traumatic according to DSM‐5 (i.e., an event of sudden and catastrophic character) and (iii) the prevalence of PTSD, AjD and cancer‐related PTSD according to DSM‐5.Results291 patients participated (response rate: 58%). Mean age was 54 years, 60% were male. 168 patients (59%) reported cancer‐related stressors, with the most frequent being cancer diagnosis disclosure (n = 58, 27%). Eight percent of reported stressors qualified as traumatic events according to DSM‐5. Five (1.8%), 15 (5.3%) and 20 (7.0%) cancer survivors met DSM‐5 criteria for current PTSD, lifetime PTSD and AjD, respectively. Among all PTSD cases, three were cancer‐related (1.1%). In addition, seven patients (2.5%) met all symptoms for cancer‐related PTSD, but not the DSM‐5 criterion for medical trauma. Considering receiving the cancer diagnosis as traumatic event, which is debatable according to DSM‐5, 38% of stressors qualified as traumatic and six patients (2.1%) met criteria for cancer‐related PTSD.ConclusionsDSM‐5 criteria enable a clear identification of traumatic events in the context of cancer. This change may inform discussions on the appropriateness of PTSD in cancer patients and facilitates its differentiation from AjD. Larger studies need to validate our findings.