In the era of Industry 4.0, consumer behavior has shifted towards smart shopping trends. Additionally, the seamless integration of online and traditional sales channels (omnichannel) is becoming a key strategy for many retailers. However, research on smart shopping behavior in this context is limited in Vietnam. Therefore, analyzing the factors influencing the smart shopping behavior of Vietnamese people in an omnichannel environment is necessary and urgent. This study aims to: Develop a model of factors influencing smart shopping behavior, Test the impact of personal, marketing stimuli, social, and relationship quality factors with retailers in an omnichannel environment. Based on the theory of relationship marketing, the proposed research model includes 4 main factor groups. The scale was developed based on previous studies and adjusted through qualitative research. Data was collected from 500 consumers via an online questionnaire, and the scale was tested using Cronbach's Alpha and EFA. The model was officially tested by multivariate regression analysis on a sample of 1100 consumers. The results show that personal factors, integrated marketing stimuli, social factors, and relationship quality all have a positive influence on smart shopping behavior. Among them, the relationship quality and omnichannel marketing stimuli factors have the greatest impact. The study contributes new findings regarding consumer behavior theory in an omnichannel context. Management implications are also drawn to help retailers develop appropriate marketing strategies to promote smart shopping behavior and improve the quality of customer relationship.