The present study aimed at investigating the relationship between environmental and individual factors and Stress of Conscience among nursing staff in psychiatric in-patient care. A questionnaire involving six different instruments measuring Stress of Conscience, the ward atmosphere, the psychosocial work environment, Perceived Stress, Moral Sensitivity, and Mastery was answered by 93 nursing staff at 12 psychiatric in-patient wards in Sweden. The findings showed that Sense of Moral Burden, Mastery, Control at Work and Angry and Aggressive Behavior were related to Stress of Conscience. We conclude that Mastery and Control at Work seemed to work as protective factors, while Sense of Moral Burden and perceptions of Angry and Aggressive Behavior made the nursing staff more vulnerable to Stress of Conscience. Future research should investigate whether measures to increase the level of perceived control and being part of decision making will decrease the level of Stress of Conscience among the staff.