Abstract The purpose of this research is to provide a model of the impact of internal marketing on the performance of the banking industry based on the data-based theory method. The research method is applicable in terms of the purpose, and qualitative in terms of the implementation method, based on the inductive approach. The statistical population of the research includes 8 experts of the banking industry, and the sampling was done in a targeted manner and the interviews continued until reaching theoretical saturation. Semi-structured interview was used in this research. To collect and analyze the data, the foundation's data theory research strategy was used. For data analysis, MAXQDA 2020 software was used to code the interviews. The results indicated that a total of 5 components of job security, training, employee motivation and satisfaction, positive communication, development and reward were identified as internal marketing features in the banking industry, and 14 components were identified and extracted in the form of causal conditions (establishing constructive interaction between employees and managers, generous rewards, employee empowerment, management support), foundational conditions (organizational leadership and management, human resource management measures, organizational culture), interventions (political climate, organizational costs), strategies (promotion of customer-oriented culture, person-job fit), and outcome (human development, value creation, increased commitment). Extended Abstract Introduction With the increasing demand for banking services in the society and the competition to maintain the interests of the country's banks, especially in the private banks, each bank, in some way or other, tries to attract people as customers within their financial system in order to benefit from the resulting benefits. Therefore, the success of all banks, governmental or non-governmental, is influenced by several factors; one of the most important of which is customer satisfaction, in order to achieve excellence in business; and this customer satisfaction is one of the basic requirements of quality management systems (Akbari, 2019). An important issue in marketing management is the relationship between internal marketing and business success; internal marketing as a construct or concept is not universally accepted. One of the key features of internal marketing is its connection with the performance of the organization (Tahmasbi et al, 2019). In the banking industry, the role of human capital in providing services is quite significant. Employees in this industry facilitate the implementation of the organization's strategies and superior performance through effective interaction with customers. Therefore, the solution to guarantee the excellent performance of the organization should be sought in the successful activation of human capital; and in order to achieve the goal of providing productive financial resources for the organization, the work should start by paying attention to the employees, that is, those who interact with customers and take care of their affairs. In this aspect of the activity of service organizations, the issue of internal marketing is raised (Naami & Mazhari, 2014). Based on this, the current research is looking for an answer to this question: What is the model of the effect of internal marketing on the performance of the banking industry based on the data-based theory method? Theoretical Framework Marketing Marketing is a set of activities and processes of creating, transferring, sending and exchanging everything valuable for customers, clients, business partners, and society as a whole. Marketing does not start with a new idea or an innovative product, but it is the beginning and end of every business, and the focus of marketing is also the customer (Hoseini et al, 2022). Internal marketing Internal marketing is defined as the use of a marketing perspective to manage the organization's human resources. To have high-quality services, employees must be motivated, which requires that internal marketing precedes external marketing because internal marketing depicts a win-win cooperation between employees and the company (Imani et al, 2020). Zamaniyan & Yazdani Rad (2023) investigated the impact of internal marketing on competitive advantage by considering the mediating roles of strategic market tendencies, brand and value in the banking sector. The results of the structural equation model test showed that internal marketing directly has a positive effect on competitive advantage. Internal marketing has a positive and significant impact on competitive advantage indirectly through the roles of strategic orientations including market orientation, brand orientation, and value orientation. Sahraei & Mafibalani (2023) investigated the role of using electronic marketing and information technology in the business of Minoo food industry during the period of economic recession. The results of the survey showed that information technology support has a positive and significant effect on the business of Minoo food industry in the economic recession. The knowledge of information technology does not have a positive and significant effect on the business of Minoo food industry in the economic recession. The managerial beliefs of marketing preparations and the implementation of electronic marketing have a positive and significant effect on the business of Minoo food industry in economic recession conditions, and information technology and electronic marketing have a positive and significant effect on the business of Minoo food industry; but with the introduction of economic recession adjustment, no significant effect was observed. Research methodology The research method is applicable in terms of the purpose, and qualitative in terms of the implementation method, based on the inductive approach. The statistical population of the research includes 8 experts of the banking industry, and the sampling was done in a targeted manner, and the interviews continued until reaching theoretical saturation. Semi-structured interview was used in this research. To collect and analyze the data, the data-based theory research strategy was used. Research findings For data analysis, MAXQDA 2020 software was used to code the interviews. The results indicated that a total of 5 components of job security, training, employee motivation and satisfaction, positive communication, development and reward were identified as internal marketing features in the banking industry; and 14 components were identified and extracted in the form of causal conditions (establishing constructive interaction between employees and managers, generous rewards, employee empowerment, management support), foundational conditions (organizational leadership and management, human resource management measures, organizational culture), interventions (political climate, organizational costs), strategies (promotion of customer-oriented culture, person-job fit), and outcome (human development, value creation, increased commitment). Conclusion The current research was conducted with the aim of providing a model of the effect of internal marketing on the performance of the banking industry based on the data-based theory method. The results of this research are consistent with the results of Kim et al, (2016), Bahmani & Iman Khan (2018), Zamaniyan & Yazdani Rad (2023), Mohammadi et al, (2022), Asayesh & Famili (2022), Mazzarolo et al, (2021), Kakai et al, (2021). Rustaei et al, (2022) stated in their research that in today's growing and competitive world among banks, the motivation of employees and their individual improvement and acceptance of their needs before the organization has become a big issue. On the other hand, in order to create a distinctive image among customers, the bank should pay much attention to the category of internal marketing and better performance of financial interest; because effective performance leads to differentiation between private banks in the eyes of customers. It is necessary to pay attention to the needs and conditions necessary to provide a suitable platform for the expansion of internal marketing and to attract the participation of employees in order to create organizational commitment among employees. According to the research results, the following suggestions were made: - Setting up training courses or holding seminars in this regard for bank managers and employees in the field of internal marketing - Surveying employees and managers regarding the level of satisfaction of internal and external customers with their performance and creating a database in this field - Updating it regularly and examining the problems of employees and managers in the field of internal marketing and making appropriate decisions to solve them.