Occupational stress is an increasingly important occupational health problem causing a significant economic lost. Petrochemical industry workers are one of several occupational groups who potentially experience high level of occupational stress. They work in high pressure environment, handling hazardous material and managing large amount of chemical energy. This was an intervention study to assess the effect of stress management intervention program based on DASS42 score. The stress management program adopted consisted of lectures on stress and stress management, video sessions, question and answer sessions, pamphlet distribution, and aerobic exercises. In assessment of effectiveness of stress management program, it was found that there were significant reduction in pre and post-intervention (immediate and one month post-intervention) with estimated marginal mean of depression score, anxiety score and stress score (p > 0.001). It indicates the needs to improve the work environment in term of decision latitude, psychological job demand, and toxic exposure. A regular short stress management program is effective in reducing some aspect of depression, anxiety and stress in this group.