This article examines the clinical concept of delusional atmosphere or mood, which denotes a predelusional state that may precede the formation of primary delusion in schizophrenia. Delusional mood refers to a global, diffuse, ominous feeling of something (not yet defined) impending. This article explores how schizophrenia spectrum patients usually experience delusional mood and it accounts for certain typical phases that tend to lead to the crystallization of primary delusion. In brief, delusional mood often involves an increase of basic affective tone, followed by an atmosphere of apprehension, free-floating anxiety, guilt, or depression, perhaps of something impending. The delusional mood becomes increasingly self-referential and eventually the world may come to be experienced as staged, artificial, or unreal. The current diagnostic manuals make no reference to delusional mood and thus it risks slipping “under the radar” or being mistaken for, for example, expressions of anxiety or depression.