Knowledge about suicide postvention (KSPV) is an important distal outcome in the evaluation of suicide prevention programs that focus on the bereaved. However, most scales are specifically tailored to the evaluation study in question and psychometric properties are often unsatisfactory. Therefore, we developed the KSPV scale. Scale properties were investigated with Rasch trees, a newly developed method in the framework of item response theory. Additionally, we provide cues for convergent validity. In summary, the scale shows satisfactory properties for assessing KSPV and could be used to evaluate suicide postvention programs more effectively.