The article describes a case of a 69-year-old patient with Parkinson’s disease, who underwent deep brain stimulation treatment and developed side effects in the form of delirium after pulse generator implantation and a psychotic disorder with delusions due to the known physiological condition after pulse generator initiation. The patient suffered an episode of psychosis with visual hallucinations and persecutory delusions that directly endangered his life. After stimulation was discontinued and antipsychotic drugs were administered on a psychiatric ward positive symptoms abated. After the mental state stabilized, motor symptoms such as upper limb tremor and gait difficulties worsened. The patient was referred for further neurological treatment.