To encourage employees to behave in an environmentally conscious manner, businesses are embracing Green HRM (Green Human Resource Management) techniques more. The purpose of these practices, which include eco-centric performance management, sustainability-focused training, and green hiring, is to encourage sustainable behaviour in the workplace. Employee ambassadorship—the idea that employees actively embody and promote green values—is crucial to the success of green human resource management. Such employee-led advocacy improves consumer trust and brand credibility while fortifying the company’s green branding. With the help of a qualitative case study of Unilever, a world leader in sustainability, this study investigates the connection between Green HRM, Employee Ambassadorship, and Green Branding. Eco-friendly hiring, training, and incentive programs that enable employees to advocate for sustainability are key components of Unilever’s human resources strategies. According to research, Unilever employees actively support sustainable business practices in addition to engaging in green behaviours, which strengthens the company’s environmental brand image. The study concludes that companies need to make strategic investments in Green HRM practices that enable staff members to serve as sustainability ambassadors, coordinating internal HR initiatives with external branding and long-term sustainability objectives, to establish a credible green brand.