The CI-NERGY Marie Curie Initial Training Network (ITN) aims to train young scientists to develop urban decision making and operational optimisation software tools to minimise non-renewable energy use in cities. The training will be carried out by a close collaboration of six of the best academic research centres and four leading industrial companies from the energy and software technology sector (Siemens, WienEnergie, EDF/EIFER, and IES). The research fellows will apply their results in two case study cities (Geneva and Vienna), which were chosen for their very ambitious sustainability goals. The CI-NERGY network will be a highly multi-disciplinary coordinated PhD programme on urban energy sustainability, covering the key challenges in cities related to a low carbon future. There is a gap in high level integrated training in the urban energy research field, which is due to the wide range of fragmented disciplines from building physics and energy supply technologies with electrical and thermal engineering up to software engineering and information technology. The CI-NERGY network wide training provided by excellent academic and industry partners from all areas of smart cities will close this gap. The impact of the network training activities will be highly noticeable for energy supply utilities, IT companies, policy makers,urban planners, researchers on sustainable urban energy systems and finally the inhabitants of cities themselves. All sectors mentioned will provide excellent career opportunities for the research fellows, who will gain excellent knowledge of the sectorial requirements by a structured secondment plan.