Introduction: Unhealthy nutrition plays an effective role in increasing non-communicable diseases. The aim of this study is to assess the experiences of patients with cardiovascular disease(CVD) risk factors, and healthcare providers working in diabetes unit of health centers, to ascertain the defeaminants of nutritional behavior based on the Health Belief Model. Materials and Methods: This qualitative study utilized the content analysis approach, conducted over a six month period in 2012, at the diabetes units of health centers, associated with Alborz University of Medical Sciences, located in Karadj- Iran. The data was collected based on individual semi-structured interviews with 50 patients and 12 healthcare providers in the diabetes unit. Data analysis was performed simultaneous with data collection, using the content analysis directed method. Results: Analysis of the data resulted in finding 54 primary codes, all of which were placed into pre-determined categories of the Health Belief model, including threat perceived, benefits and barrier perceived, self efficacy and social support. Most patients were unable to follow healthy diets on a regular or continuous basis. Conclusion: Study results demonstrate the determinants of nutrit­ional behavior as perceived by patients and healthcare providers and can help program planners in designing programs to select the most appropriate methods and applications to address these determinants in order to reduce unhealthy nutritional behavior and to eventually prevent CVDs.