Sustainability challenges call for a swift paradigm shift away from business as usual, yet there is a gap between the corporate ambition and the change needed, with an even larger gap to the implementation of this corporate ambition. Consultants act as one type of intermediary to bring sustainability into corporations to aid transitioning towards this new paradigm. Knowledge intensive business services (KIBS) firms act mainly as process intermediaries, often supporting change agents for sustainability that act inside corporates, and characterized as “deliberately pursuing (more rather than less) radical organizational change for sustainability”. Numerous KIBS firms maintain close and prolonged interactions with their corporate clients, often performing essential yet largely unseen roles in aiding change agents within those client organizations. This ‘unseen’ element also applies to consultants focusing on sustainability service offerings. The study suggests that to accelerate change towards sustainable innovation in corporates and contribute to a swift paradigm shift away from business as usual, KIBS as intermediaries should focus on engaging individuals in corporates, rather than trying to convince whole departments or teams through a standard sales pitch approach. The study also suggest that the intermediary KIBS literature on external change agents for sustainability has, to date, neglected the importance of client-intermediary relationships and business acquisition processes, instead focusing on external change agents for sustainability in already established intermediary relationships.