The main goal of the TREX Centre of Excellence (CoE) is to enable the community codes for stochastic quantum chemical simulations to successfully exploit the most advanced European computing facilities, i.e., the EuroHPC pre-exascale and exascale machines, and foster the use of supercomputers with energy-efficient accelerators (e.g., GPU) by means of state-of-the-art quantum Monte Carlo (QMC) codes, developed in Europe and internationally recognised as key algorithmic assets. This will be achieved via a co-design approach to the development of the QMC community codes in order to prepare them for the next generations of HPC hardware. In line with this goal, this document sets out an effective communication, dissemination and stakeholder engagement strategy to be implemented by the consortium during the 36 months of the project. Consistent and content-rich communication is strategic to showcase the results and impact of the TREX project. This plan has been built on a continuous set of actions of communication and dissemination campaigns for the main TREX assets, primarily the TREX community codes for advanced QMC simulations, complex scalable workflow, and training and educational activities, ensuring coverage of all stakeholders and adequate visibility worldwide. The custom-made TREX web platform is at the heart of the engagement, outreach and exploration strategy of the project, it is the technological engine behind the technical support to end-users of TREX software, and hands-on workshops to forge a new generation of code developers. Various communication and promotional campaigns are presented in this document, with detailed timelines presenting the activities that will be put in place. For each of these campaigns, specific communication, dissemination, and stakeholder engagement activities and synergies within the EU HPC ecosystem are detailed to ensure the successful achievement of the project objectives