The current prescription rate of long-acting injectable antipsychotics (LAI) is less than 1% in Korea. This study aimed to investigate the reason for LAI underuse by surveying the attitudes toward LAI among psychiatrists and patients receiving LAI. A total of 173 psychiatrists and 99 patients receiving LAI participated in the survey. Participating psychiatrists were divided into two groups according to experience with prescribing LAI to at least 10 patients. The two psychiatrist groups did not differ significantly in terms of sociodemographic characteristics and clinical practice patterns. However, the group with higher experience more frequently provided explanations of LAI to their patients and was more satisfied with the use of LAI than the group with less experience. Acceptance rates of patients to the recommendation for LAI treatment and satisfaction of psychiatrists with the outcome of LAI were also significantly higher in the group with higher experience. Psychiatrists with less experience with LAI were more negative toward LAI than patients receiving LAI as well as psychiatrists with higher experience. In conclusion, attitudes of psychiatrists toward LAI were closely related to the use of LAI. The negative attitude and reluctance of psychiatrists, rather than patient resistance, may contribute toward the underuse of LAI.