Systemic steroids are highly effective for patients with moderate-to-severe asthma exacerbations. Steroid-induced psychosis is known to be one of the adverse effects of steroid therapy, although infrequent. However, there is no reliable method of predicting steroid psychosis. We experienced the case of a 40-year-old asthmatic man who had previously taken steroids without any psychological side effect, but became acutely delirious after receiving some doses of steroids, higher than the previous doses, under a condition of emotional stress. The mean dose of prednisolone administered was 82 mg/day (1.37 mg/kg/day) for 10 days but the patient had taken two courses of steroids (0.82 mg/kg/day and 0.5 mg/kg/day, respectively) for asthma exacerbations without any psychiatric episodes during the previous year. At this time, the patient was under a condition of emotional stress related to family reasons. The asthmatic exacerbation of this case may be precipitated from sudden emotional stress and the following treatment with a high dose of steroida should be used cautiously due to the possibility of psychotic side reactions.