The chapter proposes to philosophically ground the ethics expertise in social work, starting from a series of ethics theories: utilitarian ethics, deontological ethics and ethics of virtues. During the foundation of ethics expertise we made conceptual distinctions between the theoretical and practical nature of expertise, between the ethical and the moral one, in order to justify the need for a new model of ethics expertise. In our approach, we debate the influence of such theories in the field of social services, which we consider to be representative in the context of the construction of a new model of ethics expertise, which underlies the constitutive values of social practice. The normativity of the ethical theories is extended to the level of certain different behavioural models and moral reasoning, summing up in practice the frameworks of the moral conduct the individuals can apply, when making an ethical decision, in social or organisational context, namely to determine whether the decision is morally acceptable or not.