Socio-technical systems are characterized by the interplay of heterogeneous entities i.e., humans, organizations, and technologies. Application domains such as petroleum, e-health, and many others rely on solutions based on safety-critical socio-technical systems. To ensure a safe operation of these interacting heterogeneous entities, multifaceted and integrated modeling and analysis capabilities are needed. Currently, such capabilities are not at disposal. To contribute to the provision of such capabilities, in this paper we propose SafeConcert, a metamodel that offers constructs to model socio-technical entities and their safety-related properties. SafeConcert also represents a unified and harmonized language that supports the integrated application of qualitative as well as quantitative safety analyses techniques. To support our claims we briefly report about the evaluation that was conducted and documented in the context of the EU CONCERTO project.