For a real impact on healthcare, precision cancer medicine requires accessibility and interoperability of clinical and genomic data across centres and countries. Due to the heterogeneous digitization in Europe and worldwide, the definition of models for standardised data collection and usability becomes mandatory if countries want to work together on this mission. The European Union 1+Million Genomes (1+MG) initiative, supported by the Horizon 2020 Beyond 1 Million Genome project, aims at outlining data models, guidance, best practices, and technical infrastructures for transnational access to sequenced genomes, including cancer genomes. Within the framework of the cancer-focused Working Group 9 (WP9), we developed the 1+MG-Minimal Dataset for Cancer (1+MG-MDC)–a data model encompassing 138 items and organized in eight conceptual domains, for the collection of cancer-related clinical information and genomics metadata. The 1+MG-MDC, which is the result of a multidisciplinary effort, leverages pre-existing models and emphasizes the annotation and traceability of multiple aspects relevant to the complex longitudinal path of the cancer disease and its treatment. We strived to make 1+MG-MDC easy to adopt and to be filled in, and yet comprehensive, addressing the needs of both clinicians and researchers. It will be periodically revisited and updated by the 1+MG WG9 to ensure it remains fit for purpose. We propose it as a model to create homogeneous databases, which would, in turn, guide discussions on clinical and genomic features with prognostic or therapeutic value and foster real-world data research.