Purpose: Occupational stress is a determinant risk factor for cardiovascular disease and work disability. This study aims to describe occupational stress and identify its related factors among aged security guards. Methods: A random sample of 76 aged security guards were interviewed by three research assistants. The criteria of the subjects were as follows : 50 or older male with 40 or more working hours a week working with colleagues ranged from 3 to 50. The data were collected in September, 2007 and analyzed by multiple regression using SAS Version 9.1. Results: The mean score of occupational stress among aged security guards was 47.2. The mean scores of its sub-scales were 31.3(physical environment), 33.8(occupational demand), 80.8occupational control), 44.6(interpersonal conflict), 51.3 (occupational insecurity), 53.6(occupational system), 57.5(lack of reward), and 30.3(work environment). The scores of occupational control, interpersonal conflict, and occupational insecurity were higher than the scores of Korean average occupational stress sub-scales. Significant variables affecting occupational stress and its sub-scales were work place, work type, and employment type. Conclusion: In order to reduce occupational stress among security guards, sufficient occupational control and interpersonal conflict control, appropriate reward, and employment stability should be considered. Also long working hours and work shift should be improved.