Currently, organizations are often confronted with difficulties in finding sufficient human capital with the necessary qualifications. Moroever, they consider it hard to establish a sustainable  and lasting relationship with these employees. Although the labor market has changed due to the corona crisis, this problem remains in many sectors. Therefore, it is essential for companies to position themselves as an attractive employer and, consequently, to focus on employer branding. The external aspect of employer branding (external branding) has already been extensively studied: how and what should organizations do to attract the right employees and how can they differentiate themselves from other companies. However, little is known about internal branding. Nevertheless, in the context of a sustainable HRM policy, this is extremely important. How can organizations create internal branding? How can you retain employees in a more sustainable way  through internal branding? How can you turn your own employees into ambassadors of your organization? This will be explored through case studies and through experimental research. In summary, this project aims to take a pioneering role by thoroughly examining the concept of internal branding. It thus offers an important scientific contribution to gaps in the literature regarding employer branding and sustainable HRM. The results will also have a social impact, as hardly any actions have yet been investigated to stimulate internal branding and ambassadorship.