Background: A healthy diet is one of the real modifiable factors in controlling high blood pressure. The trans theory model is the best known and applies to a variety of unhealthy behaviors such as: Hypertension, obesity, drug use, and smoking. Aim of the study: was conducted; to evaluate, the effect of application of trans-theoretical model; on diet behavior modification; among hypertensive employee; in electrical Company. Design: A quasi-experimental; design; was used. Setting: The study; was conducted; at Benha Electrical Company; in Benha City, Egypt. Sample: A purposive sample; of 70 hypertensive employee; in electrical company. Study instruments included; two tools ;used for; data collection. First: Structured interview questionnaire; concerned with socio-demographic; data and knowledge; of employees about hypertension, Diet behavior modification and Trans theoretical model (TTM). Second: Transtheoretical model of behavior changes questionnaire. Results: revealed that, 14.3 %; of studied sample; had good knowledge; pre TTM application; compare to 81.4%; of studied sample had good knowledge post TTM application for Diet behavior Knowledge. And none to 88.6% for TTM Knowledge Furthermore, there were; a highly. Significant; improvement; (p<0.000) in subtotal TTM levels. Post TTM application ' "satisfactory" responses were increased from a range of 28.6% pre TTM application, to 95.7% post TTM application. Besides, there was, high significant; positive correlation; between; total knowledge score and total score; of stages of diet behavior changes (r = 0.76, p<0.0001). Conclusion: Application of TTM for behavior modification to control hypertension in hypertensive employees was observed by decreasing blood pressure measurements and increasing employee self-efficacy experiences and behavior modification processes. However, it decreased after TTM application compared with TTM application. Recommendation: provide electrical company employees with web site for health information to improve their knowledge and diet behavior to control chronic diseases as hypertension