Recent decades have seen an increasing emphasis on linking the content and aims of science teaching to what the average citizen requires in order to participate effectively in contemporary society, one that is heavily dependent on science and technology. However, despite attempts to define what a scientific education for citizenship should ideally involve, a comprehensive set of key aspects has yet to be clearly established. With this in mind, the present study sought to determine empirically the extent of any consensus in Spain regarding the principal aspects of scientific competence that citizens should possess in order to function adequately in everyday life. This was done by means of a three-stage Delphi process involving 31 participants drawn from among leading and acknowledged Spanish scholar-scientists and engineers, researchers and private sector scientists, philosophers of science, science educators, and science communicators. The outcome of this process was a set of five aspects for which there was both consensus and stability. Several of these aspects were also found to be interrelated. There was a tendency for higher ratings to be given to aspects related to attitudes and/or values than to those referring to knowledge. It was in relation to the latter, along with other aspects concerning the nature of science, that discrepancies were observed among the different professional groups surveyed. Comparison of the present results with the content of previous reports indicates that in recent decades the ability to think critically and skills related to the interpretation of information have been considered to be important aspects for citizens to acquire as part of their scientific education. It is argued that the five key aspects identified in this study should be considered jointly in the context of school science education, since they are interrelated skills that citizens will require when tackling important issues and making decisions in various spheres of their life (personal, social, professional, etc.).