Despite the significant contribution of organizational culture research to the scientific literature in other research fields, studies investigating the culture needed to foster food safety practices remain scarce. Of the works that have been published, most have been at a conceptual level, and little is known about the development of measurement scales to assess food safety culture in onsite foodservices, one sector of foodservice. This study aimed to develop a measurement scale to assess food safety culture and tested this scale in two types of onsite foodservices, namely hospitals and schools. A mixed methods approach was used and included two research phases. In phase one, four focus groups were conducted with foodservice employees, who held non-supervisory positions, to explore factors in the workplace that helped and prevented employees from following food safety practices. Nine themes emerged as follows: 1) leadership, 2) communication, 3) self-commitment, 4) management system and style, 5) environment support, 6) teamwork, 7) accountability, 8) work pressure, and 9) risk perceptions. These themes were then used in item scale development. In phase two, a survey was conducted with foodservice employees to test and validate the developed measurement scale. A total of 582 useable survey responses were obtained and subjected to factor analysis with six factors extracted: management and coworkers support, communication, self-commitment, environment support, work pressure, and risk judgment. The six-factor structure of food safety culture showed a satisfactory level of reliability and validity. Further analysis of the survey data showed employees' perceptions on certain factors of food safety culture were significantly different across gender, age group, years of foodservice experience, time worked at current workplace, work status, and whether or not employees received food safety training. Significant differences were also found in employees' perceptions based on their workplace management system, operation type and size. Areas of strength and potential improvement of food safety culture were identified. Significant differences in employees' perceptions can guide development of interventions that support safe food handling practices in onsite foodservices. Further research is needed to confirm and validate the application of the food safety culture scale in other types of onsite foodservices.