Nurses encounter ethical dilemmas in their practice and need guidance in making relevant patient-care decisions. Nursing theory is believed to be the best source of such guidance. The aim of this paper is to describe the ethical dimension in nursing theory. A literature review shows the intricate relationship between ethics and nursing, yet there is lack of elaboration of ethical features in nursing theories. The identified elements of the ethical dimension include ethical theories and principles, values, ethical practice issues, moral reasoning and contextual factors. Criteria for the development and evaluation of the ethical dimension are presented, with an example using a middle range theory. The ethical components pertinent to a nursing theory need to be made explicit if theory is to guide practice. Nursing scholars are invited to elucidate the ethical dimension in their theories in order to enhance moral reasoning and provide a framework for ethical practice.